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ELECTEO 

Astronomical Atlas, 



DESIGNED FOE 



SCHOOLS, ACADEMIES AND LADIES' SEMINARIES, 



EXPLANATORY NOTES, QUESTIONS AND ANSWERS. 



BY REV. J. W. SPOOR, A. M. 

ROCHESTER, N. Y. 



FULLY ILLU STR J^ T E D . 






'THE HEAVENS DECLARE THE GLORY OF GOD, AND THE FIRMAMENT SHOWETH HIS HANDIWORK, DAY UNTO DAY ITTTERETH 
SPEECH, AND NIGHT UNTO NIGHT SHOWETH KNOWLEDGE."-PSA. XIX : 1. 




ALBANY, N. Y. 

WEED, PARSONS AND COMPANY, PUBLISHERS, 

1874. 




6P 



/ 



Entered, according to act of Congress, in the year eighteen hundred and seventy-three, 

Br the Author, 

JOSEPH W. SPOOR, A. M., 

in the office of the Librarian of Congress, at Washington. 



PREFACE 



The design of the author in presenting this work to the public is : To 
meet a great want in giving instruction in the interesting science of Electrical 
as well as Physical Astronomy. 

Hitherto, the knowledge of Astronomy has only been taught in our Univer- 
sities, Colleges and High Schools, and in them in a very limited manner, hence, 
those in our public schools have been entirely deprived of all knowledge of 
this useful branch of education. 

Teachers of public schools have heretofore felt great embarrassment on 
introducing this branch of instruction in such schools, because of their incom- 
petency to impart instruction to their pupils in the science, hence their objec- 
tion to its introduction. This objection is entirely removed in presenting this 
work. It not only presents to the teachers an easy method of gaining instruc- 
tion in the science, but an easy and pleasing way of imparting the same to 
their pupils. 

It is the purpose of the author to present to the public an elementary work, 
and to bring this instruction within the reach of children from twelve to sixteen 
years of age, and so simplify and arrange it, that they can learn it as easily as 
they can learn Geography. 

He has also adopted the catechetical form of instruction as a more popular 
method than the topical, because better adapted to their youthful comprehen- 
sion, and they can the more easily retain the knowledge sought. 

Some years since, he constructed and designed to publish a Diagram of the 
Solar System, to aid in the instruction of this science, for which the highest 
commendations were given by some of the most Scientific and Learned in 
the Universities and Colleges in this country. 



PREFACE. 



This Diagram is pronounced the best of any yet exhibited to the public, 
from the fact that it is the only one that presents the whole Solak System to 
the eye at one view, and represents the orbits according to the true scientific 
angles by which they cross the plane of the Ecliptic. 

The author is happy to announce that this Diagram is published and may 
be found in the front portion of the Atlas, and a description of it and its uses 
accompanies its introduction. 

The author, having for many years investigated the laws of Electricity, and 
finding them intimately connected with Astronomy, in the evolutions of the 
Planets, hopes to be able to throw attractions around the study of Astronomy 
which will not fail to interest the lovers of science as much in this as in any 
branch of education ever presented to the scientific world. 

He claims for this work a set of Diagrams and Illustrations exhibiting 
the most recent discoveries and observations made in this science down to the 
present time. 

The progress of Astronomy is so rapid that almost all Text-Books are 
behind in this particular. 

With these intentions and observations the work is published and pre- 
sented to the public. 

In preparing this work the Author has also freely consulted the following 
works among others: "Mitchell," "Guiilemin," "Schellen," "Brewster," 
"Burritt." 

AUTHOR. 



m 




INTRODUCTION 



Accompanying this work is a Diagram, which, at the time of recitation, when necessary, 
can be spread open before the pupils that they may the more clearly apprehend the instruc- 
tion imparted by it. A description of its design and use will now be given : 

The object of this is to aid the teacher the more clearly to illustrate, and the scholar 
the more easily to apprehend the instruction to be received of this interesting science. 

The Planetary System embraces the Sun, the Planets which move around him in their 
respective orbits, the Satellites or Moons connected with their respective primaries, together 
with the Asteroids and Comets. The Diagram exhibits at one view and in an oblique form 
this entire structure of the Solar System. 

Other Solar charts now in use present only parts of this System to the eye at the same 
time, and represent the orbits as lying on the same plane and in true circles, and give a very 
imperfect view of the manner in which the Planets are enlightened by the Sun during the 
different months of the year. 

The design of this Diagram more particularly is to exhibit and explain the true cause 
and philosophy of equal Day and Night ; of the changes of the Seasons ; why we have a differ- 
ence in the length of Day and Night ; the evident cause of the Eclipses, both Solar and Lunar ; 
what produces the changes of the Moon, or, in other words, why we behold the Moon assum- 
ing so many different phases ; and gives a comprehensive view of the movements of the 
heavenly bodies. 

The Diagram also represents the Sun as the grand common center around which all the 
Planets move in their respective orbits, at different distances from the Sun, and the inclina- 
tion of their axes. It also represents the Moon and Secondaries in their orbits, as they are 
moving around their respective primaries ; and represents all as having their enlightened sides 
turned toward the Sun, their great central luminary. It represents, also, the relative magni- 
tude of the planets, and their comparative distances from the Sun. It shows the elongated 
orbits of the Comets — their respective nodes and longitudes. 

There is also a tabular view showing the distance of each planet from the Sun ; the 
diameter of each planet and its time around the Sun representing the length of its year ; the 
time required to revolve around its axis, showing the length of its day ; the inclination their 
orbits make to the Ecliptic ; the inclination of their axes to their own orbits ; their density and 
the eccentricity of their orbits, and the difference in their Polar and Equatorial diameters. 

Having given the design of the accompanying Diagram, I will proceed to give a 
description of the several parts explanatory of the principles it is designed to teach, with 
suitable questions and answers. 



TESTIMONIALS. 



University of Eochbster, 1ST. Y. 

January 6th, 1861. 
I have examined with much interest and pleasure 
a Diagram of the Solar System, exhibited by Dr. 
J. W. Spoor, of this city. It is one of the best I 
have ever seen, and when the modifications which 
he proposes to make are perfected it will be the 
very best. It will greatly aid the young student of 
Astronomy in forming a just conception of the 
order and arrangement of the bodies of our system, 
and will give him a tolerably good idea of the 
physical peculiarities of each body. 

J. F. QUINBY, 
Prof, of Math, and Nat. Phil. 



University of Eochester, 

January 11th, 1862. 
As an improved means of communicating im- 
portant knowledge and of diffusing it among the 
people, the Diagram of the Solar System, by Dr. 
Spoor, deserves high commendation. I gladly 
unite in the judicious statement of Prof. Quinby, 
and cordially commend it to the schools and their 
teachers and to the people in general. 

C. DEWEY, 
Prof, of Chemistry. 



Madison University, 

November 15th, 1861. 

Dr. J. W. Spoor has exhibited to us, to-day, a 

Diagram of the Solar System, which he is about to 

publish for the use of institutions of learning, 

especially of Common Schools, Academies and 



Ladies' Seminaries. We have been much interested 
in the examination of the Diagram, and cannot 
hesitate in expressing our judgment that its plan 
and execution are, in several important respects, 
greatly superior to those of any Diagrams of the 
kind to which our attention has been called. It 
cannot fail to facilitate, in a high degree, the study 
of the very interesting branch of knowledge for 
whose illustration it is designed, materially aiding, 
as it must, the teacher in communicating correct 
notions, and the pupil in apprehending them, in 
respect to the characteristic and leading facts 
appertaining to our Solar System. 

GEO. W. EATOX. 
Pres. of Madison University. 
[Signed by every member of the Faculty.] 



Hamilton College, 
November 18th, 1861. 
Dr. J. W. Spoor : 

Dear Sir: I was pleased with your idea of 
preparing a Diagram of our Solar System for the 
use of schools. There can be no doubt but a good 
Diagram may be used with great advantage in 
acquiring elementary notions of Astronomy; it 
will assist both the teacher and the pupils. It is 
also obvious that a very great amount of valuable 
information can be brought within a very small 
compass; nearly the entire statistics of the Solar 
System may be presented on such a Diagram as you 
propose to publish. * * * 

Yours, respectfully, 

0. EOOT, 
Prof, of Math, and Nat. Phil. 



T$. B. — Instruction to Teachers in the use of Diagram, pages 91-92. 



CONTENTS 



PAGE. 

LESSON I. — Circle Defined — Circumference — Diameter — Arc — Radius — Degrees 18 

LESSON II. — Semi-Circles — Quadrant — Circles — Equator — Ecliptic — Tropics 13 

LESSON III. — Lines: Curved, Straight, Parallel— Point— Surface — Ellipse — Its Diameter 14 

LESSON IV. — Angles : Right, Acute, Obtuse — Triangle 14 

LESSON V. — Astronomy — Heavenly Bodies — Solar System — Sun — Size Compared with the Earth — Distance 

from the Earth — Terms Aphelion and Perihelion — Its Weight — How Known — Physical Nature — Appearance, 15 

LESSON VI. — Hypothesis — Element — Electricity — Its Discovery — By Whom — Diversity of its Operation 16 

LESSON VII. — Sun — Relation to the Solar System — Its Electrical Power — Developed in Attraction and Repulsion 

— Position Confirmed by R. A. Proctor and Other Eminent Astronomers — Pervading of all things by Electricity, 16 

LESSON VIII. — Sun's Motion— Time Revolution — How Know it Revolves — Its Axis — Spots on its Disc — 

Accounted For — Drummond Light Compared with the Sun 17-20 

LESSON IX. —Solar Prominences — Time of Appearance — Production — Duration — Height — Appearance of Jets 

— Scenes from Harvard College — Spots — Passage over Disc — Appearance — Uniform Time 21 

LESSON X. — Dimensions — Compared to the Globe — Measurements of Schroeter — Of Sir W. Herschel — Of Cap- 
tain Davis — Remark — Physical Organization of the Sun — Views of Sir W. Herschel — Of Kerchoff — Of Sir 
John Herschel — Why Vary in Appearance — Way the Sun Turns on its Axis — Do all the Planets and Constel- 
lations Turn the Same Way ? — Evidence of their Revolution from West to East — Time of Revolution of Sun — 
Inclination to Ecliptic , 22-23 

LESSON XL — Planets — Why thus called — Division — Primary — Secondary — Equilibrium of Motion — Law of 

Attraction and Repulsion — Law explained 23 

LESSON XII. — Distribution of Secondary Planets — Interior Planets — Exterior — Their Conj unctions — How shine — 

Distinguished From Stars 24 

LESSON XIII. — Apparent Motions of the Sun, What Called — How Caused — The Daily Phenomenon Connected with 
the Apparent Motions of the Sun — Changes in the Points of Rising and Setting — Point of Culmination — Sol- 
stices and Equinoxes — Note — Ecliptic — Coincidence with the Plane of the Earth's Orbit — Intersection of the 
Circle of the Celestial Sphere and the Orbit of the Earth — Obliquity of the Ecliptic 24-26 

LESSON XIV. — Mercury — Situation — Rate of Motion — Time of Revolution — Indications — Diameter — Inclina- 
tion of Orbit to Plane of Ecliptic — Inclination of Axis — Time of Revolution on its Axis — Uniformity of Appear- 
ance i 26-27 

LESSON XV. — Transit — Primaries Making Transits — When Occur — Condition of Earth and Planets when it 
Occurs — Ecliptic — Nodes — Months in which Transits of Mercury Occur — Why ? — Called What ? — First 
Transit — Time of Others 27-28 

LESSON XVI. — Mercury — Density — Heat — Solar Light — Velocity — Why so Great — Conjunctions — Names — 

Distances from Earth in Different Conjunctions — In what Months Most Favorably Seen 28-29 



PAGE. 

LESSON XVII. — Venus — Situation — Distance from Sun — Time of Revolution — Indication — Inclination of Orbit 
with Ecliptic — Time of Revolution on Axis — Indication — Rate of Motion — Inclination of Axis with Plane of 
Orbit — How Distinguished 30 

LESSON XVIII. — Satellites — Venus and Mercury Satellites of the Sun — Evidence — How Discovered — What 

Names — Diameter — Appearance — Similarity to Moon — Conj unctions — Appearance in Each 30-31 

LESSON XIX. — Venus — Different Changes — Diameter — Difference in Size — Transit — Time When — Benefit 

Derived — Appearance in Transit — Time of Transit — Time of Last One — Occur When — Time of Last When 

Next — Peculiarity of Twentieth Century — How far Recede from Sun 31-32 

LESSON XX. — Mountains of Venus — Height — Schroeter's Statement — Volume — Light Compared to that of the 
Earth — Distance from the Earth — In Different Conjunctions — Circumference of Orbit — Phases — Evidence of 
What — How Change Her Appearance 32-33 

LESSON XXL — The Earth — Situation — Form — Spherical — Evidence — Not Perfect — Proved — Difference of 

Diameter — Position Important 33-35 

LESSON XXII. — Revolution of the Earth — Time — Indication — Changes of Seasons — Axis — Position — Time of 
Revolution on Axis — Production — Cause of its Revolution on its Axis — Explanation — Illustration — Law 
Equally Essential in all Planets — Problem Solved — Distance from Sun — Circumference of Orbit — Rate of 
Motion — Inclination of Axis 35-36 

LESSON XXIII. — Time — How Reckoned — Uniformity — Advantage Derived — Remarks — Plane of Ecliptic Illus* 

trated — Kepler's Law — Location of Sun in Earth's Orbit — Shape of Orbit 36-37 

LESSON XXIV. — Causes of their Change — How far is the Axis of Rotation Inclined to Plane of Ecliptic — Time of 
Year — Equal Day and Night — Why Then — Why Day — Why Night — The Result of the Revolution of the 
Earth on its Axis — Points Called — Way of the Revolution 37 

LESSON XXV. — Difference of Time in the Days and Nights Explained — Summer Solstice — Why So Called — Dis 
tance the Sun Shines Beyond the North Pole — Situation of South Pole — Movements of the Sun Further 
Explained 38 

LESSON XXVI. — Length of the Days and Nights Considered — Number of Seasons — What Called — Zodiacal 
Light — Time of Appearance — In what Part of the Heavens — Form of the Light — Compared with Milky Way 
— Not Seen at all Seasons — When Only — In what Months — Favorable Nights — Zodiac — What is it — Descrip- 
tion of Belt— How Occupied — Location of Ecliptic — Term "Constellation" — By Whom Used — Why Called 
Zodiac — What Use is made of the Signs of the Zodiac — Names — Correspondents of these — The Earth in Cap- 
ricorn — Where then is the Sun Vertical ? 39-40 

LESSON XXVII. —What Does This Show — Why Warmer on the 21st of June — Sun Further Away — Difference 
in Diameter — Difference of Time in Equinoctial Points — Nearest the Sun Perihelion — Farthest Aphelion — 
Motion Faster at Which — Density — Variation of Equinoctial Points — Difference of Diameter — Discovery — 
Weight at the Poles and the Equator — Cause of This 41 

LESSON XXVIII. — The Moon — Form of Orbit — Perigee — Apogee — Mean Distance — Inclination of its Orbit to 
Plane of Ecliptic — Lunar Days in a Year — How much of Moon Seen — Illustrated — Evidence of any Life on 
the Moon — Result if there Were — ■ Any Seas, Lakes, Rivers — Any Winds or Tornadoes 42 

LESSON XXIX. — Phases of the Moon — Explanation of them — First appearance where — At what time — Way of 
Revolution — Degrees in twenty-four hours — Her changes Explained — ■ Time of Full Moon — Position now in 
Respect to Sun — Why in Opposition 43-44 

LESSON XXX. — Appearance in the First Half of her Orbit — Appearance in the Last Half — What Remarkable in 
her History — When called New Moon — When Full Moon — Relation to the Earth — Satellite — Time of Revo- 
lutions — What Called — How Near the Earth — Revolutions in a year — Synodic and Sidereal Revolution 45-46 

LESSON XXXI. — Physical aspect of the Moon — Appearance Variable — Cause of this — Appearance Through Tel- 
escope — Rough — Mountains — Compared to those of the Earth — -Peculiar Formations — Ring Mountains — 
Description — Eclipses — Cause of Eclipse — Philosophical Cause Given 46-48 



CONTENTS. 



PAGE. 

LESSON XXXII. — Eclipse — When occur — Explained — When they cannot occur — Result, if the Orbits of the 
Earth and Moon were on the same Plane — Cause of an Eclipse of Sun — When only occur — Tides — How pro- 
duced — Time of Spring Tides — Why ? — Effect of Sun — That of Sun less than Moon — Why ? 48-50 

LESSON XXXIII. — Planet Mars — Location — Appearance ; To the Naked Eye — Distance from Sun — Time around 
it — Indication — Time of Revolution on Axis — Indication ? — Diameter — Inclination — Exterior — Why ? — Re- 
semblance to Earth — Changes of Climate — Divisions of Land and Water — Geography Similar — Mars Probably 
Uninhabited — Circumference of Orbit — Distance from Earth — Opposition — Where looked for — Position of 
the Earth — Appearance of Mars 51-52 

LESSON XXXIV. — When take place — Cause of brilliancy — Distance one side of Orbit — Inclination — Rate of 
Motion — Light, compared with that of Earth — Difference of Diameters — Density, compared with the Earth — 
Difference of Weight — Ratio from Sun of the Orbits of Planets described — Rapid Changes — White Spots — 
Snow Zones 52-53 

LESSON XXXV. — The Minor Planets — What are they ? — Number — Space occupied — Kepler's impression — Not 
witnessed in his Day — Two Hundred Tears after — Discovery Made — Four Found — Ceres, Pallas, Juno and 
Vesta 53 

LESSON XXXVI. — Ceres — Time and by whom discovered — Estimate by Sir W. Herschel — Diameter — Distance 
from Sun — Time around it — Inclination — Appearance in Size and Color— Pallas — Time and by whom Dis- 
covered — By whom Measured — Distance from Sun — Time around it — Inclination — Appearance as to Size and 
Color — Juno — Time and by whom Discovered — By whom Estimated — Appearance as to Size and Color — Dis- 
tance from Sun — Tims around it — Inclination of Orbit — Vesta — Time when and by whom discovered — Com- 
parison with the other Minor Planets — Diameter — Distance from Sun — Time of Revolution — Inclination of 
Orbit — Description of all nearly the same 54-56 

LESSON XXXVII. — Planet Jupiter — Situation — Why Distinguished — Distance from the Sun — Time around it 
— Indication — Diameter — Time of Revolution on its Axis — Indication — Circumference of Orbit — Rate of 
Motion — Effect of Motion on the Weight of Bodies on his Surface — Weight of Bodies on his Surface com- 
pared with their Weight on the Earth — Cause of Difference — Satellites — Variable Appearance — Observations 
of Mr. Dawes 57 

LESSON XXXVIII. — Satellites of Jupiter — Number — Names — Diameters — Distances — and Revolutions — 
Eclipses — Number per Month — Eclipse of Sun effected by them — Inclination of the Axis of Jupiter to Plane of 
his Orbit — Plane of Orbit to Plane of Ecliptic — Eccentricity of Orbit — Solar heat compared with Earth 58-59 

LESSON XXXIX.— Observations of Astronomers — Appearance of Belts — What known — Situation — How esteemed 
by Astronomers — Uniformity considered — Other peculiarity of appearance — Accounted for — Difference of Jupi- 
ter's Diameters 59-60 

LESSON XL. — Saturn — Situation — Distance from Sun — Time round it — Indication — Diameter — Revolution on 
Axis — Indication — Inclination of Axis to its Orbit — Inclination of Orbit to the Ecliptic — Eccentricity of its 
Orbit — Difference of Diameters — Solar Light compared with that of Earth — Rate of Motion — Density — Dif- 
ference of Weight — Why one of the most magnificent Planets — Rings and Moons 60 

LESSON XLI. — Rings of Saturn — Situation of them — Revolution — Detached — How known to be Separate — 
Distance from Planet to Interior Ring — Breadth of it — Width between Rings — Thickness of Rings — Consists 
of what — How determined — Importance of them to the planet 61-62 

LESSON XLII. — Circles not True — Centers coincide with the Center of Planet — Gravity of These Rings — Import- 
ance to the Stability of the System of Rings — Moons of Saturn — Number — Seldom Seen — Revolve with the 
Rings — Respective Distances from Saturn — Inclination of their respective Orbits to the Plane of Saturn — 
Eclipses of these satellites — Seldom Suffer — Respective Sizes 62 

LESSON XLIII. — Uranus — Situation — Distance from Sun — Time of Revolution round the Sun — Diameter — 
Time of Revolution on Axis not known — Inclination of Orbit — Rate of Motion — Light compared with that 
of the Earth — Density — Eccentricity of Orbit — Difference of the Weight of Bodies on the Earth and the Sur- 
face of Uranus — Satellites of Uranus — Number — Respective Distances and Periodic Times — Their Variation 
in Revolution — Size of them — Seldom suffer Eclipse" 62-63 



10 CONTENTS. 



PAGE. 

LESSON XLIV. — Neptune — Situation — Orbit — Distance from Sun — Revolution round it — Diameter — Rate of 
Motion — Inclination of Orbit to the Ecliptic — Time on Axis unknown. — One Satellite — Situation — Time around 
the Primary — Indication 63-65 

LESSON XLV. — Comets — Where found — Appearance — ■ Why called Comets — Appearance Varied — Distinguished 

from Planets — Form of Orbits— How are they distinguished 65-67 

LESSON XLVI. — Elements of Comets — Orbits — Number computed — Classes Elliptic — Long Periods — Shorter 
Periods — Number Reappeared — They are generally named after their discoverers — Size of Orbits — Compara- 
tive inclination of them — Way of Revolution 67-68 

LESSON XLVII. — Comparative Periods of Comets — Course of Revolution of Comets whose Orbits have been ascer- 
tained — One- half of them in .opposite directions — Inclinations very diverse — Velocity compared with Planets 
in general — Far Greater — Number Discovered 68 

LESSON XLVIII. — Celebrated Comets — Comet of 1811 —Dimensions — Aphelion distance — Halley's Comet — 
How distinguished — Appeared in many previous years — Comet of 1843 — How distinguished — Encke's Comet 

— Period of Return — What peculiar in its return — Donati's Comet appeared in 1858 — Effect produced — 
Wonder of Many — For what distinguished — Law by which they are Governed — Description of its Opera- 
tion — Longitude of the Parhelion of the Comet 1858 — Longitude of its Node — Longitude of the Parhelion of 

the Comet 1862 — Longitude of its Node — Rapidity of Comets — Cause for it 69-71 

LESSON XLIX. — What supposed to be — How produced — What called — Why so called — How many seen in 
an Hour — Showers of Stars — When exhibited — At what Intervals — Hombold and Bompland's Observations — 
Arago's Observations — Regular Periods of Showers — Intersection of the Earth and the Orbit of the Comet — 
Brilliant display accounted for — Light produced by their rapid flight through the Atmosphere — Annual Exhibi- 
tion of Meteors in August — Regularity accounted for — Schiaparrelli's discovery 72-74 

LESSON L. — Remarks — Constellations — Design in presenting an Elementary Work — Not Extensive or Critical — 
In considering the Stellar Universe — The Object in Presenting Constellations — How differ from Planets — In 
Twinkling and Scintillating — Description of a few — Exhibited in the Northern Sky — The best time of 
observing them — What Called — Why Called Northern Circumpolar — North Pole point of Revolution — Consid- 
eration of Maps — MAPI. — Constellation Great Bear, Ursa Major — Time of appearance — Number of Stars 
contained in the Group — Figure formed Large Dipper — Two Northern Stars Pointers — Why called thus — 
Polaris the object to which they point — Revolution — 2d Constellation — Little Bear — How Distinguished — 
Contains Polaris — North Pole Star — A Fixed Star — Why called Fixed Stars — They revolve in the Universe — 
Great Velocity — Time its Light travels down to us — 3d Constellation — Gassiopia — Location — Form of Figure 

— Sprawling" W" — Cepheus and Draco — Where Located — Nothing Striking — Perceus elsewhere 74-76 

LESSON LI. — Constellation Orion —Time of favorable appearance — Names of the Constellations — Distinguished — 
The most beautiful Constellation in the Sky — Whale better seen elsewhere — -Stars of Belt of Orion — The Bull 
or Taurus — Situation — How Marked — Cluster called Hyades — Another cluster called Pleiades — Another Con- 
stellation called Gemini, or the Twins — Where Situated — Names of the most important Stars — Castor and 
Pollux — Little Dog — Location — How Distinguished — Procyon and Gomelza — Great Dog — Situation — Name 
of the largest — Sirius Brightest Star — Rate of Motion — Time it takes to reach the Earth — Distance estimated 

— Diameter — Constellation The Whale — Situation 76-77 

LESSON LII. — MAP III — Constellation Virgo — Favorable time for Inspection — When seen in the Heavens — 
How known — Large Constellation — One Star of first Magnitude — Spica its name — Leo, or the Lion — Where 
situated — How easily known — Shaped like a Sickle — An inverted figure 5 — Regulus the largest — On the 
Ecliptic — Gamma — Where situated — 3d Constellation — Hydra — Situation —Form of Serpent Swimming from 
East to West— Stars small 77-78 

LESSON LIII.— MAP IV— Constellation Bootes — Time of Appearance — In June — Situation in the Heavens — 
The Brightest Star Arcturus — Where found — On Meridian — Shape Parallelogram — Four bright Stars — Form 

— Coffin — Another group East — Like a boy's cap — Northern Crown — Large Constellation further East — Her- 
cules — Size — What figure — Two Quadrila/terals — Opinion respecting the course of the Solar System — Drift- 
ing toward Hercules , 78 



CONTENTS. 11 



LESSON LIV. — MAP V— Constellation The Swan — Time favorable — Where found — Overhead — Figure formed 

— Large Cross — Principal Star at foot ■ — Albireo — Multiple Star — The Eagle — Where situated — South of 
Swan — How distinguished — A Large Star — Atair — Pegasus — Where located — North-east of Eagle — Figure 
of these Stars — Perfect Square — The most Western found — Head of Andromedia — The Lyra — Where situated 

— West of Swan and North-west of Eagle — What Star Prominent — Vega — What completes the group — 
Four faint Stars 79 

LESSON LV. — MAP VI — Constellation Perseus — When favorably seen— December — Where found — Meridian 

— Well North in Milky Way — Figure of chief Star — Turkish Sword — Bent at the point — What near the 
point — Mass of Telescopic Stars, very beautiful — One marked — Called Algol — Constellation Aries or Ram — 
Where seen — South of Perseus — Figure formed of Principal Star — Right Angled Triangle — Point in the 
Seasons marked —Vernal Equinox — What Constellation South of the Ram — Whale — Figure easily traced — 
Pentigon of Stars 80 

LESSON LVI. — Contrast of the Distance of the Sun and that of the Fixed Stars from the Earth — Remarks. — Rate 
of motion of ball from an Armstrong gun — Time taken to reach the Sun — Time for the sound of the Explosion 
to reach the Sun — Prof. Mendenhall on nervous sensation — The infant burns its finger by touching the Sun — 
Time necessary to realizing the sensation — Earth on disc of Sun — Require a large telescope to discover it — 
Distance of Sun from Earth compared to that of the Fixed Stars — The Fixed Stars, Suns — Do not remain 
unmoved — Revolve in the Universe like other Planets — Principal Suns named — Why appear small — Dis- 
tance cannot be computed by miles — Velocity of light considered — Miles per second — Number in 24 hours — 
At this rate how long to reach the nearest Fixed Star — 61 Gygni — Vega — Sirius — ■ Ursa Majoris — Arcturus 

— Polaris and Cappella — These do not shine by reflection — Suns in other Systems 81-82 

LESSON LVII. — Light — What is it — Views of Sir Isaac Newton — Flowing out from the " Orb of Day " — Recup- 
eration, or Waste Away — Space embraced in Solar System — Rapidity of light — At this rate how long will it 
take to fill the Space — Does not remain Stationary — Moves on in Circle — Light changes its Polarity — Is 
received back to the Sun — How does the Sun remain undiminished and brilliant as ever — By recuperation in 
the return of it to the Sun — No indication of a continued work of creation — Principle illustrated by 82-84 

LESSON LVIII. — Attraction of Gravitation — Attraction of Gravitation defined — Seen in the power the Sun exerts 
over the Planets — All under the magnetic influence of the Sun — Planets rendered Magnets by the electrical 
power of the Sun — This inherent magnetism controls the Satellites — This magnetism called Terrestrial Mag- 
netism — Subject Terrestrial Magnetism or the Magnetism of the Earth — This magnetism accounted for — Sun a 
great Galvanic Reservoir — Heat of Torrid Zone — Compared with Temperate and Frigid Zone — Intensity of the 
heat of the Sun — Three hundred times greater than any point on the Earth's surface — Sir John Herschel's 
estimate - Note 84 

LESSON LIX. — Terrestrial Magnetism — Continued — Torrid regions — More deeply electrified — Result — They 
are positive — Polar negative — Reasons for this — Effect produced upon the Earth — Earth filled with elec- 
tricity becomes a magnet — This Terrestrial Magnetism seeks and flows out of the Magnetic Poles — Points of 
the greatest cold — Both North and South — Result — Consequence of the combined action of these forces — 
Explanation — Effect of these currents on the Needle — Magnetic Poles and Geographic not the same — At the 
Geographic no effect on the needle — Reasons why — Note 85-86 

LESSON LX. — Aurora Borealis — How produced — Caloric and Electricity the same — Currents within the Earth 
naturally seek the point of the greatest cold, flow out and form a lambent waving light — Called Aurora — ■ This 
illustrated — Historic evidence — Captains Parry and Ross — Their testimony — The ultimate conclusion — This 
clearly explained — Power of Terrestrial Magnetism controls the Moon — On the principle of Attraction and 
Repulsion — The same law by which the Sun governs the Planets and they their Secondaries in the Solar System, 86-87 

LESSON LXI. — Attraction and Repulsion — Subject defined — Law governing — Ultimate particles have opposite 
polarities — Law manifest — Laws of the whole are the laws of its parts — By this rule only can Attraction and 
Repulsion be accounted for — Magnetism and Electricity considered the same agent — Galvanism differs only in 
the mode of exhibition — Experiment — Result from passing a current of Galvanism through Soft Iron ; change 
the poles of Battery — Change the polarity of the Iron — This explained — Distinction of polarity manifest in 
the direction of the current — This explained — Positive and negative end to every thing — Running electricity — 
The inward current always negative — The outward current positive — Remark 87-88 



12 CONTENTS. 



PAGE. 

LESSON LXII. — Attraction and Repulsion — Continued — Another mode of illustration — Current of Galvanism 
passed around Steel — Result — A magnet — Cut the Steel in pieces — Each arranged with the same polarity 
of the whole — Logical inference — Conclusively evident — How illustrated — By the atmosphere and ocean. . 88-89 

LESSON LXIII. — Attraction and Repulsion — Continued — This theory explained — Two magnets — Effect when 
Positive and Negative are presented to each other — They attract — Result when like polarities are presented — 
Entirely opposite ; they now Repel each other — Two Positives repel — A Positive and Negative attract each other 
■ — Scientific World challenged to give a clear explanation on any other principle — A body charged with electricity 
has an outward current, and will attract a negative with an inward current — Clearly shown by the magnets — 
These laws applied in the Attraction and Repulsion — How accomplished 89-90 

Elements of the Solar System 94 

Elements of the Minor Planets 94-96 



ELECTRO-ASTRONOMICAL ATLAS. 



DEFINITIONS. 



LESSON I. 

Analysis. — Circle Defined — Circumference — Diameter — Arc — Radius — Degrees. 




Q. What is a Circle ? cseeFig.i.] 
A. A figure bounded by a curved line, every 
point of which is equally distant from the center. 
Q. What is the circumference of a circle ? 
A. The curved line that bounds it. 
Q. What is the diameter ? 



A. A line passing through the center of a cir- 
cle, and terminated by the circumference. 

Q. What is any part of the circumference 
called? 

A. An Arc. 

Q. What is the Radius ? 

A. A straight line drawn from the center to the 
circumference. 

Q. How is the circumference of a circle di- 
vided ? 

A. Into 360 degrees. 

Q. Into how many equal parts is a degree 
divided ? 

A. Sixty equal parts, called minutes. 



LESSON II, 



Analysis. — Semi-Circles — Quadrant - 

Q. What is a Semi-circle ? 
A. One-half of a circle, or 180 degrees. 
Q. What is a Quadrant ? 
A. A quarter of a circle, or 90 degrees. 
Q. How many kinds of circles are there ? 
A. Two : great and small. 
Q. What is a great Circle ? 
A. A circle whose plane divides the sphere into 
two equal parts. 



Circles — Equator — Ecleptic — Tropics. 

Q. What is a small Circle ? 

A. A circle whose plane divides the sphere into 
two unequal parts. 

Q. Mention the principal great Circles? 

A. Equator and Ecliptic. 

Q. Mention the principal small Circles ? 

A. The Tropic of Cancer, the Tropic of Capri- 
corn, and the two Polar Circles. 



14 ELECTRO-ASTRONOMICAL ATLAS. 


LESSON III. 


Analysis. — Lines : Curved, Straight, Parallel — Point — Surface — Ellipse — Its Diameter. 


Q. What is a Line ? 


Q. What is a Surface % 


A. It is that which has length without breadth 


A. It is that which has two dimensions — length 


or thickness. 


and breadth. 


Q. What is a Curved Line ? 


Q. What is an Ellipse ? 


A. One that continually changes its direction. 


A. It is a figure bounded by a curve, from any 


Q. What is a Straight Line % 


point of which, if straight lines be drawn to two 


A. A line which has the same direction at 


fixed points within, called the Foci, the sum of 


every point. 


these lines will be the same. 


Q. What are Parallel Lines % 


Q. What is the longest diameter of an Ellipse 


A. Lines that extend in the same direction, and 


called? 


are at the same distance from each other at all 


A. Major Axis. 


points. 


Q. What is the shortest diameter called % 


Q. What is a Point ? 


A. Minor Axis. 


A. It is that which is conceived to have neither 




length, breadth or thickness, but position only. 




LESSON IV. 


Analysis. — Angles : Right, Acute, Obtuse — Triangle. 




A. An angle formed by a straight line meeting 


/""Obtuse! Right Angle. 




a perpendicular line. 








/ tS&^l 




Q. What is an Acute Angle \ 




\ / 




A. An angle less than a right angle. 


f 


\ / 




Q. What is an Obtuse Angle. 


H 






A. One greater than a right angle. 




Q. What is a Triangle % 


Fig. 2. 


A. A figure bounded by three sides. 


Q. What is an Angle ? csee Fig.20 


Q. What is a Sphere or Gflobe 1 


A. The opening of two lines that meet in a 


A. A round body, every part of the surface 


point. 


being equally distant from a point within, called 


Q. Name the different kinds of Angles % 


the center. 


A. Right, Acute, and Obtuse. 


Q. What is a Hemisphere % 


Q. What is a Right Angle ? 


A. Half a sphere, — hemi meaning half. 



PLATE 1. 




THE SUN 



ELECTRO-ASTRONOMICAL ATLAS. 



15 



LESSON V. 

Analysis. — Astronomy — Heavenly Bodies — Solar System — Sun — Size Compared with the Earth — Distance from the Earth • 
Terms Aphelion and Perihelion — Its Weight — How Known — Physical Nature — Appearance. 



ASTRONOMY. 

Q. What is Astronomy ? 

A. It is that branch of science which treats of 
the heavenly bodies. 

Q. What are the names of the heavenly 
bodies \ 

A. The Sun, Planets, Satellites, Comets and 
Stars. 

solar system:. 

Q. What is the Solar System ? 

A. The Solar System is composed of these 
heavenly bodies, moving in harmony round the 
Sun, as their common center. 

Q. How many bodies are embraced in the 
Solar System % 

A. There are one hundred and sixty-four. 

Q. How are they divided ? 

A. There are the Sun, eight primary planets, 
twenty-one secondaries, and one hundred and 
thirty-four Asteroids, or Minor planets. 

THE STXN". 

Q. What is the Sun ? 

A. A vast, brilliant globe, around which the 
planets, their satellites, and comets revolve. 

Q. What is the size of the Sun compared with 
the planets surrounding it ? 

A. The Sun is by far the largest of the heavenly 
bodies, being more than five hundred times as 
large as all the planets taken together. 

Q. What is its magnitude when compared with 
that of the Earth ? 

A. The Sun is equal to 1,400,000 globes the 
size of the Earth. 

Q. Can we form an adequate conception of its 
vast dimensions ? 



A. It is impossible for the human mind to 
form an idea of its vastness. 

Q. What is the diameter of the Sun ? 

A. Its real diameter is 852,900 miles. 

Q. What is the distance of the Sun from the 
Earth ? 

A. Recent investigations show the distance, 
when the Earth is in Aphelion, to be 93,000,000 
miles ; but when it is in Perihelion, it is 90,000,000 
miles, the mean distance being 91,500,000 miles. 

Q. What is meant by the term Aphelion % 

A. That point of the orbit which is farthest 
from the Sun. 

Q. What is meant by the term Perihelion : 

A. That point which is nearest the Sun. 

Q. How does the weight of the Sun compare 
with all the planets, satellites and comets of the 
Solar System 1 

A. About seven hundred and fifty times as 
heavy as all of them taken together. 

Q. How do we ascertain its weight ? 

A. From the power of its attraction. 

Q. What is known of the physical nature and 
constitution of the Sun ? 

A. Various are the theories of astronomers 
respecting its physical nature and constitution. 
The recent and most reliable hypothesis is, that 
the nucleus of the Sun is an incandescent solid 
or liquid mass. 

Q. How does it appear to us when seen 
through a telescope? 

A. It presents the appearance of an enormous 
globe of fire, frequently in a state of violent agi- 
tation or ebullition. 



16 



ELECTRO-ASTRONOMICAL ATLAS. 




LESSON VI. 

Analysis. — Hypothesis — Element — Electricity — Its Discovery — By Whom — Diversity of its Operation. 

A. Electricity is also derived from another 
Greek word, Electore, which signifies "beaming 
sun." 

Remark. — This seems to indicate that the ancients supposed 
the Sun to be the fountain of this subtle fluid. 

Q. What led him to make the discovery ? 

A. He ascertained that the amber, when rubbed, 
acquired the power of attracting to itself certain 
light bodies surrounding it. 

Q. How can this interesting phenomenon be 
illustrated by the student without this amber ? 

A. By taking a stick of sealing wax and 
brushing it briskly with a piece of silk, or 
woolen cloth, and passing it over small pieces of 
paper. 

Q. Is Electricity uniform in its manifestation ? 

A. Infinite wisdom has constituted Electricity 
a mighty agent, in various ways, his "wonders 
to perform." 

Q. In what manner more particularly is it 
revealed ? 

A. It is not simply manifest in the thunderbolt, 
but in the agitative power of galvanism ; in the 
permeating influence of magnetism ; in a univer- 
sal flood of light, and in the all-pervading mani- 
festations of heat. 

Q. What are other modified representations of 
this same imponderable principle ? 

A. The attraction of gravitation and cohesion. 



Fig. 3. 

ELECTRICITY. 

From the fact that the Sun is the source of all light, heat, and 

life in the realm of nature, and that light and heat are component 

parts of Electricity, therefore, the Hypothesis is entertained that 

the Sun is constituted with the all-pervading element Electricity. 

Q. What element naturally flows out of the 

Sun? [See Fig. 3.] 

A. Electricity. 

Q. What is Electricity ! 

A. Electricity is an imponderable fluid, eman- 
ating from the Sun. 

Q. When and by whom was Electricity discov- 
ered? 

A. It was discovered 600 years before the 
Christian era, by Thales, a celebrated Grecian 
sage of the city of Miletus in Ionia. 

Q. How did he make the discovery ? 

A. He detected it in a substance called amber, 
which, in the original Greek, is called Electron, 
from which is derived the term Electricity. 

Q. Is it derived from any other word ? 



LESSON VII, 



• Sun — Relation to the Solar System — Its Electrical Power - 
firmed by R. A. Proctor and Other Eminent Astronomers • 



Developed in Attraction and Repulsion ■ 
- Pervading of all Things by Electricity. 



Relation of the Sun to the Solar System. 
Q. What relation does the Sun hold to the 
entire Solar System ? 



A. The Sun is the great fountain of electricity, 
from which emanates, as from a galvanic battery, 
all the power necessary, under the established 



ELECTRO-ASTRONOMICAL ATLAS. 



17 



electrical laws of attraction and repulsion* to 
govern the motion of the planets in their diurnal 
and annual revolution around the Sun. 

Q. What other principle does it produce ? 

A. It produces the vivifying principle of both 
animal and vegetable life, all chemical changes 
in the realm of nature, and is the active and effi- 
cient agent, both in decomposition and recompo- 
sition of the organic structure of men and 
animals. 

Q. Is there any part of the Solar System in 
which this principle is not manifest ? 

A. There is no department of the entire Solar 
System in which this imponderable principle does 
not exert a quickening and controlling influence 
or power. 

* In a letter written the _ZV. Y. Herald, from Cleveland, 0., Jan. 
28, 1874, Richard A. Proctor holds this language on the evolution 
of the earth : " During all these years, she has been gathering up 
a few .... chips scattered about the mighty workshop in 
which the giant workmen Attraction and Repulsion had fash- 
ioned the Solar System." Other eminent astronomers have re- 
cently confirmed me in my position as to the law of Attraction 
and Repulsion governing the planetary world. 



Q. Is this element all-pervading in its influence 1 
A. It permeates every thing — from the largest 

planet, Jupiter, to the smallest particle of sand 

upon the sea shore. 



Remark. — What Pope said of the Divine es- 
sence is as truly said of this all-pervading prin- 
ciple : 

" It warms in the sun, 

Refreshes in the breeze, 
Glows in the stars, 

And blossoms in the trees ; 
Lives through all life, 

Extends through all extent, 
Spreads undivided, 

And operates unspent." 

Note. — We should never lose sight for a moment of the 
great self-existent principle we call Deity, whose Attributes are 
Omniscience, Omnipresence, Omnipotence and Eternity ; who cre- 
ated all things, and established the universe, composed probably 
of hundreds of solar systems like our own, and sent them spin- 
ning through infinite space, balanced and controlled in perfect 
harmony, under those electrical laws by which He governs all 
things in His vast and infinite domain. 




LESSON VIII. 

Analysis. — Sun's Motion — Time Revolution — How know it Revolves — Its Axis — Spots on its Disc — Accounted For - 

mond Light Compared with the Sun. 

Motion of the Sun. 

Q. In what time does the Sun revolve on its 
axis? 

A. Twenty-five days, eight hours and nine 
minutes. 

Q. What proof have we that the Sun turns on 
its axis ? 



Drum- 



A. By the motion of certain dark spots on its 
disc. 
Q. What is the axis of the Sun ? 
A. An imaginary line on which it revolves. 
Q. What is meant by the disc of a body ? 
A. The circular illuminated surface. 



18 



ELECTRO-ASTRONOMICAL ATLAS. 



Dark Spots on" the Sun. 
Q. When and by whom were the dark spots on 
the disc of the Sun discovered ? 
A. By Galileo in the beginning of the year 1611. 



Q. Since that time has the Sun always pre- 
sented a spotted disc ? 

A. From the year 1676 to the year 1684 the 
Sun presented an unspotted disc. 




Q. Do they always take the same direction over 
the Sun's disc? 

A. They do not. Sometimes they seem to move 
across it in straight lines ; at others, in curved 
lines. Sometimes upward, as they cross from 
east to west ; at others, they incline downward. 

Q. What causes these changes % 



A. They are owing to the fact that the axis of 
the Sun is inclined to the Ecliptic ; so that as we 
view the Sun from different points in the earth' s 
orbit, the direction of the spots must necessarily 
vary. 

The following diagram will serve to illustrate 
this: 




Fig. 5. 



ELECTRO-ASTRONOMICAL ATLAS. 



19 



The annexed diagram will still further illus- 
trate the cause of the change of direction of the 
solar spots : 

V-^ ^^ ^=^/ 




Fig. 6. 



Q. How are the spots on the disc accounted 
for? 

A. The atmospheres surrounding the Sun, being 
made up of the bright scintillations of electricity, 
which radiate from within, become so ex- 
ceedingly brilliant and luminous, that when 
at any time an opening appears in them, 
and the main body is seen, though incan- 
descent, yet in contrast with the dazzling 
corruscations surrounding it, the nucleus, or 
mass, appears in spots, dark and opaque. 

The forms of the spots, as shown by the 
drawings placed before the reader, are most 
varied. The penumbra most frequently 
reproduces the principal contours of the 
umbra, and often presents a great variety 
of shades, when examined with considerable 
magnifying powers. On the exterior edges 
of the penumbra, the grey tint seems generally 
the deepest, either by the effect of contrast with 
the brilliant portions that surround it, or because 
in reality it possesses at these points a more 
decided tint. 



Pig. 7 affords a striking example of this aspect 
of the penumbra. 

This spot presents the peculiarity, not at all 
unfrequent, that the dark umbra is divided into 
several fragments by luminous bridges, spanning 
it, as it were, from one side of the penumbra to 
the other. 

The umbra itself is far from offering an uniform 
black tint. In reality it always presents the 
appearance of varied shades, as if the penumbra 
and umbra were mingled, and mixed up their 
tints in varied proportions. 

[We owe to the Rev. W. R. Dawes the discov- 
ery that the umbra is but a darker kind of pen- 
umbra ; for under the best conditions of air and 
instrument, he has found within some umbras a 
much darker portion — which he calls the nu- 
cleus. This he finds to be of the most intense 
blackness ; but in saying this we must warn our 
readers that such a word as applied to the Sun 
is comparative only. Sir J. Herschel has shown 



W:MM 




Fig. 7. -WILLOW LEAF. 

Bun-spots, showing Umbra, Penumbra, and Luminous 

Bridges. (Nasmyth.)j 

that a ball of ignited quicklime, in a Drummond's 
oxyhydrogen lamp, which itself gives out an 



apparently near approach to sunlight, when pro- 
jected on the Sun appears as a Hack spot. So 
that the Sun-spots, properly so called, may not 
be so black after all !] 

The transits of Mercury, moreover, over the 
Sun's disc have taught us that the umbra is less 
dark than the unilluminated face of a planet. 

We shall now speak of the real dimensions of 
the spots, the successive changes which they 
undergo, and what astronomers call their " proper 
motion," that is, their actual movement on the 
Sun' s surface in any direction. 

Q. What effect do you say these exceedingly 



bright scintillations of electricity have upon the 
appearance of the nucleus of the Sun % 

A. When these openings are made, the mass or 
body of the Sun, although under the most vivid 
incandescence, appears dark in comparison to 
the luminous envelope which surrounds it. 

Q. How does the most brilliant light of which 
we have any knowledge compare with the light 
of the Sun % 

A. The Drummond light, the most powerful, 
when held between our vision and the Sun, pre- 
sents a dark spot. 



If we imagine that on the surface of the dark 
nucleus there are formed from time to time gaseous 
masses, incandescent by reason of their high tem- 
perature ; or again, if there exist on the same sur- 
face centers of volcanic disturbance, the eruptions 
proceeding from these 
craters, piercing and 
tearing away success- 
ively the two interior 
atmospheres of the 
Sun, would produce 
holes of the greater or 
less extent, openings 
through which the 
central nucleus or the 
overlying umbra 
could be seen. These 
openings, therefore, 
should present gen- 
erally the form of an 
irregular cone, 
widened at the upper 
part, exposing at its 
center the solid and 
obscure part of the 
Sun, and all around 
this the cloudy atmos- 
phere of a greyish 
tint. Hence, black 
spots, surrounded 
with penumbra. 

The Sun revolving 




on its axis brings a spot nearer to the center, 
hence gives us a more direct view of the opening, 
and we discover more of the dark body. Again, 
the nucleus will disappear as it passes by the center, 
until we only can see the side of the opening, 
and in a short time 
the penumbra will 
also pass from our 
view. 

But it may happen 
that the opening thus 
made in the photo- 
sphere will be smaller 
than that in the 
cloudy stratum. In 
this case the black 
nucleus will be alone 
visible, and it is thus 
that a spot without 
penumbra is ex- 
plained. If, on the 
contrary, the rupture 
in the first envelope 
closes up before the 
photosphere, then the 
obscure body will be 
invisible, a circum- 
stance which easily 
explains penumbra 
without a nucleus. 



Explanatii 



of sun-spots on Wilson's hypothesis : a a, photosphere ; b b, cloudy stratum ; A, spot with nucleus (umbra) and penumbra ; 
B, nucleus (umbra without penumbra) ; C, penumbra without nucleus (umbra). 



PLATE H. 




KARVXRC CCLLE6E OSSSRVATOKY la'i 



English miles L. 



SOLAR PROMINENCES. 

J f V s 9 »L 



PLATE IE. 




SOLAR PROMINENCES 

English milis l '9 ip H *9 W W ' 



ELECTRO-ASTRONOMICAL ATLAS. 



21 



LESSON IX. 

Analysis. Solar Prominences — Time of Appearance — Production — Duration — Height — Appearance of Jets — Scenes from 

Harvard College — Spots — Passage over Disc — Appearance — Uniform Time. 



Solar Prominences. 

Q. What phenomenon is often revealed when a 
total eclipse of the Snn occurs ? 

A. There are manifest certain solar promi- 
nences. 

Q. What is the general appearance of the solar 
prominences ? 

A. They originate in brilliant jets, either verti- 
cal or oblique. 

Q. How are these solar prominences produced ? 

A. They are produced by incandescent mole- 
cules, or emanations of the electrical element from 
the Sun. 



Q. How long do they remain ? 

A. There is a great difference in their duration ; 
sometimes they remain only a few moments ; at 
others, they continue for several days. 

Q. To how great an elevation do these often 
arise ? 

A. Sometimes to the height of eighty thousand 
miles. 

Q. What is there peculiarly interesting in these 
illustrations ? 

A. The varied appearance of these brilliant 
jets, some straight, some oblique, and others 
rising and then falling again on the Sun, like jets 
of our fountains. — See plates II and III. 




Q. Which way do these spots pass over 
disc of the sun % 

A. They pass from east to west. 

In illustration (Fig. No. 9), describe the 
of the spot just entering upon the sun's 



Q. 

form 
disc. 

A. 
beinj 

Q. 

A. 



It appears oval in form, the greatest length 

at right angles to its motion across the sun. 

Does its form continue the same ? 

In proportion as the spot approaches the 
centre, it widens, so that it becomes nearly circu- 
lar, and as it passes off the western portion of the 



sun, it assumes the same forms, only reverse in 
the order. 

Q. How long do these spots remain visible % 

A. About fourteen days. 

Q. Is this length of time ascribed to all of them % 

A. Their time is usually uniform. 

Remark.— So uniform is their time, that just 
fourteen days from the time the spot disappears 
on the western border, it again reappears on the 
eastern, often changed in form, it is true, but 
generally recognizable. 



22 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON X. 

Analysis. — Dimensions — Compared to the Globe — Measurements of Schroeter — Of Sir W. Herseliel — Of Captain Davis — Re- 
mark — Physical Organization of the Sun — Views of Sir W. Herschel — Of Kerchoff — Of Sir John Herschel — Why Vary in 
Appearance — Way the Sun Turns on its Axis — Do all the Planets and Constellations Turn the Same Way ? — Evidence of 
their Revolution from West to East — Time of Revolution of Sun — Inclination to Ecliptic. 



Q. Are the dimensions of the spots uniform ? 

A. They are extremely varied as to size. 

Q. How will they compare to our globe ? 

A. It is not uncommon to see them with their 
surface larger than the earth. 

Q. How extensive was one measured by 
Schroeter ? 

A. He measured one which was equivalent to 
sixteen times the surface embraced by a great 
circle of our Earth, or four times the entire super- 
ficies of our globe. 

Q. How great was its diameter ? 

A. Nearly four times the diameter of the Earth, 
that is, more than twenty-nine thousand miles. 

Q. What was the size of a spot measured by 
Sir W. Herschel % 

A. It consisted of two parts, the diameter of 
which was not less than fifty thousand miles. 

Q. How large were some observed by Captain 
Davis in 1839 \ 

A. The most extensive was not less than one 
hundred and eighty-six thousand miles in its 
greatest length, and the surface embraced about 
25,000,000,000 miles. 

Remark. — The question as to what is the phys- 
ical organization of the Snn is one on which as- 
tronomers have entertained various opinions, and 
to which they have failed, thus far, to give a satis- 
factory answer. The Sun appears to some to be 
surrounded by an ocean of inexhaustible flame, 
with dark spots of enormous size now and then 
floating on its surface. 

Q. AVhat views were entertained by Sir W. 
Herschel ? 



A. He supposed the Sun to be a solid, dark 
body, surrounded by a vast atmosphere, almost 
always filled with luminous clouds, occasionally 
opening, and disclosing the dark mass within. 

Q. What are the views expressed by Kerchoff? 

A. The idea entertained by him was, " that the 
Sun is an incandescent solid, or liquid mass," by 
which he means that its nucleus has the appear- 
ance of being white heated, the vapors of which 
form the atmospheres ; the denser and lower one 
being luminous, from the incandescent particles 
that float into it. 

Q. What were the views expressed by Sir John 
Herschel respecting the brilliant atmosphere 
enveloping the Sun ? 

A. He contended that the gaseous, brilliant, 
atmospheric representations arose from the elec- 
trical magnetism of the Sun. 

Q. Why do the spots vary in their appear- 
ance? 

A. The varied appearance of these spots de- 
pends upon the changes of temperature in these 
atmospheres, giving rise to tornadoes and other 
violent agitations. The descending currents pro- 
duce the various openings which are dark, be- 
cause filled with clouds of various condensation. 

Q. In what direction does the Sun turn on its 
axis? 

A. From west to east. 

Q. Do all the planets and satellites revolve in 
the same direction ? 

A. All of them except the satellites of Uranus 
and Neptune ; they revolve in the opposite direc- 
tion. 



PLATE IV. 




WEED. PARSONS &CO.,ALBANY,N: 



.TOLLC, PMDTO-IITH. 



COMPARATIVE DIMENSIONS OF THE SUN. THE PLANETS 

AND THEIR SATELLITES. 



ELECTRO-ASTRONOMICAL ATLAS. 23 


Q. Eow is it evident that planets, etc., revolve 


A. At the rate of 14,400 miles in an hour. 


from west to east ? 


Q. What is the inclination of the axis of the 


A. By the order of the signs of the zodiac. 


Sun to the Ecliptic % 


Q. How fast does the Sun revolve in its orbit % 


A. Seven degrees and twenty minutes. 


LESSON XI. 


Analysis. — Planets — Why thus Called — Division — Primary - 


— Secondary — Equilibrium of Motion — Law of Attraction and 


Repulsion — Law Explained. 


The Planets. 


Equilibrium of the Motion of the Planets. 


Q. What are planets* 


All acknowledge that God created the planets and set them 


A. Dark bodies revolving aronnd the Sun. 
Q. From whence do they derive their name % 
A. From the Greek word Planatis, meaning 


rolling in their respective orbits, and that he constituted certain 
laws, by which they are continued in their revolutions ; hence 
we lay down the hypothesis, that they are continued in their 
revolutions by the electrical law of attraction and repulsion. 


wanderer. 

Q. Why was this term applied to these dark 
bodies ? 

A. Because they change their positions in the 
heavens, while the fixed stars maintain the same 


Q. How are these planets balanced and kept 
in their respective orbits ? 

A. By the immutable law of attraction and 
repulsion ; in other words, by centripetal and cen- 
trifugal force. 


relative position. 

Q. How are the planets divided % 
. A. Into primary and secondary planets. 

Q. Mention the primary planets % 

A. Mercury, Yenus, the Earth, Mars, Jupiter, 
Saturn, Uranus and Neptune. 


Q. What is the origin or foundation of the law 
of attraction and repulsion % 

A. This law has its origin in the electrical 
power the Sun exerts over the planets. 

Explanation. — I. Two positives repel each other. II. A posi- 
tive and a negative attract each other. 


Q. Why are they called primary planets \ 
A. Because they revolve around the Sun. 
Q. Why are the others called secondary plan- 


The Sun is the fountain of all electricity to the 
planetary system, therefore always positive in his 
nature. 


ets. 

A. Because they revolve around their prima- 
ries, and with them around the Sun. 

Q. How many secondary planets are there \ 


The planet drawing near the Sun becomes posi- 
tive, and is repulsed ; receding from the Sun be- 
comes negative, and is drawn again toward the 
Sun. 


A. Twenty-two. 





24 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON XII. 

Analysis. — Distribution of Secondary Planets — Interior Planets — Exterior - 

From Stars. 



■ Their Conjunctions — How Shine — Distinguished 



Distribution of Secondary Planets. 

Q. How are the secondary planets distributed 
among the primaries ? 

A. The Earth has one ; Jupiter four ; Saturn 
eight ; Uranus eight, and Neptune one. 

Q. What planets revolve within the orbit of the 
earth ? 

A. Mercury and Venus. 

Q. What are they called % 

A. Interior planets. 

Q. What planets revolve without the orbit of 
the Earth ? 

A. Mars, Jupiter, Saturn, Uranus and Nep- 
tune. 

Q. What are these planets called ? 

A. Exterior planets. 

Q. Why is this distinction of qualification 
made % 

A. Mercury and Venus are called interior be- 
cause they are but a short distance from the Sun, 
and are seldom seen ; and the other planets are 



called exterior because they are seen at all dis- 
tances from the Sun. 

Q. What are the planets lying without or be- 
yond the orbit of the Earth called % 

A. Exterior planets. 

Q. How many conjunctions have they \ 

A. They have one conjunction and one oppo- 
sition each. 

Q. When are they in conjunction % 

A. When they are beyond the Sun and in range 
with it and the Earth. _ 

Q. When are they in opposition % 

A. When in range with the Earth and Sun, and 
the Earth is between them and the Sun. 

Q. What causes the planets to shine % 

A. The reflection of light received from the 
Sun. 

Q. How may they be distinguished from the 
stars ? 

A. Their light is steady, while the light of the 
stars appears to twinkle. 



LESSON XIII. 

Analysts. — Apparent Motions of the Sun, What Called — How Caused — The Daily Phenomenon Connected with the Apparent 
Motions of the Sun — Changes in the Points of Rising and Setting — Point of Culmination — Solstices and Equinoxes • Note — 
Ecliptic — Coincidence with the Plane of the Earth's Orbit — Intersection of the Circle of the Celestial Sphere and the Orbit 
of the Earth — Obliquity of the Ecliptic. 



Apparent Motions of the Sun. 
Q. How many apparent motions around the 
Earth has the Sun ? 
A. He has two. 
Q. What are they called \ 
A. They are diurnal and annual. 



Q. Which way does he appear to revolve in his 
diurnal motion. 
A. From west to east. 
Q. Which way in his annual motion ? 
A. From east to west. 
Q. How are these changes produced % 



ELECTRO-ASTRONOMICAL ATLAS. 



25 



A. The diurnal motion is caused by the rota- 
tion of the earth on its axis, and the annual by 
the revolution of the earth around the Sun. 

Q. How often, and at what seasons of the year 
does the Sun appear to rise exactly at the east 
point of the horizon and set at the west point % 

A. Twice each year ; about the 20th of March 
and the 23d of September. 

Q. What is the meridian altitude of the Sun ? 

A. The highest point to which the Sun appar- 
ently rises above the horizon. 

Q. During what time does the Sun's meridian 
altitude increase ? 

A. From March 20th till June 21st, and the 
points at which the Sun rises and sets move from 
the east and west toward the north. 

Q. At what time of year does the meridian alti- 
tude of the Sun diminish % 

A. From June 21st till September 23d, and 
meanwhile the points of rising and setting move 
back toward the east and west. 

Q. Does the meridian altitude vary at other 
times in the year ? 

A. The points of the rising and setting of the 
Sun, from September 23d till December 22d, move 
toward the south, and the altitude decreases 
also from December 22d till the 20th of March, 
the points of rising and setting move backward 
toward the east and west, and the meridian alti- 
tude increases. 

Q. At what points of time does the Sun seem 
to reach his culmination ? 

A. On the 21st of June and the 22d of Decem- 
ber. 

Q. What are these points called ? 

A. They are called solstices. 

Q. What are the points at which the culmi- 
nation of the Sun coincides with the celestial 
equator called ? 

A. They are called equinoxes. 



Q. Why called equinoxes % 

A. Because the days and nights are equal. 

Note. — From this it is seen there is a constant movement of 
the points of rising and setting alternately from north to south, 
and a constant variation, up and down, of the point of culmina- 
tion, except that the Sun culminates at the same altitude for 
several days, about the 21st of June and the 22d of December. 
These two stationary points of culmination are called the sol- 
stices. 

Q. What is the Ecliptic ? 

A. It is the great circle of the celestial sphere 
in which the Sun appears to revolve around the 
Earth every year. 

Q. How does the plane of the Ecliptic coincide 
with the plane of the Earth' s orbit \ 

A. The great circle of the celestial sphere is in- 
tersected by the Earth's orbit. 

Q. What is the inclination of the axis of the 
Earth to the plane of its orbit ? 

A. It is sixty-six and one-half degrees. 

Q. Then at what point do the Ecliptic and 
equinoctial cross each other ? 

A. At an angle of twenty-three and one-half 



Obliquity of the Ecliptic. 
The inclination of the Earth' s axis to the plane 
of the Ecliptic causes the equinoctial to depart 
23° 28' from the Ecliptic. This angle made by 
the equinoctial and the Ecliptic is called the 
Obliquity of the Ecliptic. 

Let the line A A 
represent the axis of 
the Earth, and B B the 
poles or axis of the 
Ecliptic. Now, if the 
line A A inclines to- 
ward the plane of the 
Ecliptic, or, in other 
words, departs from 
the line B B to the 
amount of 23° 28', it is 
oovious that the plane 
of the equator, or 
equinoctial, will de- 
part from the Ecliptic 
to the same amount. 
This departure, shown 
by the angles C C, con- 
stitute the Obliquity of 
the Ecliptic. 

Hitherto, we have considered these great pri- 
mary circles in the heavens as never varying their 




Fig. 10. — Obliquity op the Ecliptic, 



26 



ELECTRO-ASTRONOMICAL ATLAS. 



position in space, nor with respect to each other. 
But it is a remarkable and well-ascertained fact 
that both are in a state of constant change. We 
have seen that the plane of the Earth' s equator is 
constantly" drawn out of place by the unequal 
attraction of the Sun and Moon acting in different 
directions upon the unequal masses of matter at 
the equator and the poles ; whereby the intersec- 
tion of the equator with the ecliptic is constantly 
retrograding — thus producing the precession of 
the equinoxes. 

Q. What are the points opposite the Ecliptic 
where it crosses the equinoctial called ? 

A. They are called Equinoctial points, or 
Equinoxes. 



Q. How are they distinguished ? 

A. The one which the Sun passes in March is • 
called the Veenal equinox ; that which it 
passes in September is called the Autumnal 
equinox. 

Q. What are the two points opposite the Eclip- 
tic, at which the Sun is farthest from the equinoc- 
tial, called? 

A. They are called Solstitial points, or Sol- 
stices. 

Q. How are they distinguished % 

A. The one north of the equinoctial is called 
the Summer Solstice ; the one south of it the 
Winter Solstice. 



LESSON XIV. 



- Mercury — Situation — Rate of Motion — Time of Revolution — Indications — Diameter — Inclination of Orbit 
Plane of Ecliptic — Inclination of Axis — Time of Revolution on its Axis — Uniformity of Appearance. 



Mercury. 

Q. Which is the nearest planet to the Sun ? 

A. Mercury. 

Q. How far is it from the Sun ? 

A. Thirty-seven million miles. 

Q. What is its rate of motion around the Sun ? 

A. One hundred and ten thousand miles an 
hour. 

Q. How long does it take Mercury to make his 
flight around the sun ? 

A. Eighty -eight days. 

Q. What does this indicate ? 

A. The length of his year. 

Q. What is the real diameter of Mercury % 

A. Two thousand nine hundred and fifty miles. 



Q. What is the inclination of the plane of his 
orbit to the plane of the Ecliptic ? 

A. Seven degrees. 

Q. What is the inclination of its axis to the 
plane of its orbit % 

A. Seven and one-third degrees. 

Q. How long does it take Mercury to turn on 
its axis ? 

A. Twenty-four hours and six minutes. 

Q. What does this indicate % 

A. The length of his day. 

Q. Is he always uniform in his appearance ? 

A. He is not ; he presents different phases like 
the moon ; sometimes a crescent form, then gib- 
bons : at other times a full face, see rigs, u and 12. 





ELECTRO-ASTRONOMICAL ATLAS. 


27 


Let us speak first of 






from henceforward 


its form. Mercury, in 




. ">v 


characterizes it more 


the course of one of 




^ * X \ 


and more, until it is 


its oscillations, pre- 




••> ) ) 


only visible as a fine 


sents phases entirely 




luminous thread. 


analogous to those oi 




^* 


We give some of these 


our Moon. It is at 






phases. The progress- 
ive increase of its 
apparent dimensions 
is also shown in exact 
proportion. The 
same appearances are 
observed, but in in- 
verse order, when 
Mercury is observed 


first a luminous disc, 
nearly circular, which 




Fig. 11. 
Phases op Mercury when Seen After Sunset. 


by degrees is reduced 
on the side toward 
the east, until not more 
than a half-circle is 
visible at the period 




(<«•• 


of its greatest appar- 






during the period in 


ent distance from the ^— — 




which he is a morning 


Sun; the crescent 


Fig. 12. 
Phases op Mercury, when Seen Before Sunrise. 


star. 




LESSON XV. 




Analysis. — Transit — Primaries Making Transits — When Occur — Condition of Earth and Planet 


when it Occurs — Ecliptic — 


Nodes — Months in which Transits of Mercury Occur — Why ? — Called What ? — First Transit — Time of Others. 


Transits 




A. They must be on the same side of the Eclip- 


Q. What is a transit ? 




tic and the Earth, on the same line of its nodes. 


A. The passage of a planet 


between the Earth 


Q. What is the Ecliptic 


% 


and the Sun and apparently over his disc. 


A. The Ecliptic is the 


plane of the Earth's 


Q. Which of the primary 


planets have been 


orbit ; or the great circle the Sun appears to de- 


known to pass over the Sun's 


disc. 


scribe annually among the stars. 


A. Mercury and Venus. 




Q. What are nodes ? 




Q. When can a transit never occur ? 


A. The points at which 


a planet's orbit crosses 


A. When the interior planet is in or very near 


the plane of the Ecliptic. 




the Ecliptic. 




Q. When do all transits of Mercury take 


Q. When a transit takes place, what must be 


place ? 




the condition of the Earth and the planet % 


A. In the months of May and November. 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. Why? 

A. Because the nodes of Mercury are on each 
side of the Ecliptic, and passed by the Earth in 

these months. 




Fig. u 

Transits of Mercury over the Sun, 1° the 12th November, 1861, 3° the 
5th November, 1868. 



Q. What are these months called ? 
A. They are called node months. 

Note. — The Earth passes the ascending node of Mercury in 
November, and the descending node in May. The former of 
which is in the 16th degree of Taurus, and the latter in the 16th 
degree of Scorpio. 

Q. When did the first trahsit of Mercury take 
place ? 

A. The first ever observed took place Novem- 
ber 6, 1631. 

Q. How many more have transpired since? 

A. Thirty-two. 

Q. When did the last transit occur ? 

A. November 4, 1868. 

Q. How many will take place in this century ? 

A. Four— In May 6, 1878 ; November 7, 1881 ; 
May 9, 1891, aDd in November 10, 1894. 



LESSON XVI. 



Analysis. — Mercury — Density — Heat — Solar Light — Velocity — Why so Great ? — Conjunctions — Names — Distances from 
Earth in Different Conjunctions — In what Months Most Favorably Seen. 



Density and Heat or Mercury. 

Q. What is the density of this planet ? 

A. About that of lead. 

Q. What is the intensity of his heat ? 

A. It is supposed to be so great that water 
would be rapidly distilled into vapor, and that it 
would dissipate every volatile compound. 

Q. What is its solar light, compared with that 
of the Earth? 

A. It is seven times greater than that of the 
Earth. 

Q. What is said of the velocity of this planet ? 

A. It is said to be the swiftest moving planet 
yet discovered. 



Q. Why does he move swifter than any other 
planet ? 

A. Because being nearer the Sun than any 
other planet, the electrical power of the Sun, in 
attraction and repulsion, is far greater ; therefore, 
he must of necessity move swifter, and the central 
force and circular motion must be equal to retain 
the planet in its orbit. 

Conjunctions of Mercury. 

Q. How many conjunctions has Mercury ? 

A. Two. 

Q. What are they called ? 

A. Superior and Inferior. 



ELECTRO-ASTRONOMICAL ATLAS. 



29 




Q. When and why is he said to be in his infe- 
rior conjunction? 

A. When he is between the Earth and Sun, and 
because he is then in range with them. 

Q. When and why is he in his superior con- 
junction ? 

A. When beyond the Sun, and in range with it 
and the Earth. 

Q. How far is Mercury 
from the Earth ? 

A. When in his infe- 
rior conjunction it is 
fifty-eight million miles. 
Q. How far when in 
his superior conjunc- 
tion? 
A. One hundred and 
(schroeter.) thirty-two million miles. 

Q. What months are most favorable for ob- 
serving this planet ? 

A. In the months 
of March or April, 
and in August or Sep- 
tember, when its great- 
est elongation hap- 
pens. 

Q. Why is it not 

easily seen in winter ? 

A. On account of 

its low altitude above 

tne IlOriZOn at SUnriSe Crescent of Mercury, snowing irregularities on the terminator and the truncation of 

the Southern Horn. (Schroeter.) 



Fig. 14. 
Equatorial Band of Mercury 




and sunset. 

Q. Why can it not be seen in summer ? 

A. The long twilight prevents our seeing any 
small object in the heavens. 

The great proximity of Mercury to the solar 
rays renders the observation of the planet some- 



what difficult ; very little, therefore, is known of 
its surface. One diligent observer, Schroeter, at 
the end of the last century, was able, however, to 
observe some dark bands on its disc (fig. 14), 
which he considered as an equatorial zone ; it 
was from the direction of these bands that he 
deduced the inclination of the axis of rotation. 

Besides this, during the crescent phases, many 
observers (Schroeter, Beer and Madler) have seen 
indentations which make the line of separation 
of light and shade appear jagged ; they also 
observed that the southern horn of the 
crescent was truncated (fig. 15). These mark- 
ings were not always visible, but disappeared, 
to show themselves anew at intervals, the pe- 
riodicity of which has enabled us to determine 
the period of rotation of Mercury. They evi- 
dently indicate the existence of high mountains, 
which intercept the light of the Sun, and of val- 
leys plunged in shade, which lie near the 
parts of the surface 
of the planet then il- 
luminated. 

Schroeter, when ex- 
amining Mercury dur- 
ing its transit over the 
Sun on the 7th of May, 
1799, saw, or believed 
that he saw, on the 
black disc of the plan- 
et a luminous point. 
It has been concluded 
from this observation, which has not, how- 
ever, been confirmed, that there exist on the sur- 
face of Mercury active volcanoes. This would 
be another analogy between the physical consti- 
tution of this planet and that of the Earth. 



30 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON XVII. 



Analysis. — Venus — Situation — Distance from Sun — Time of 
Time of Kevolution on Axis — Indication — Hate of Motion — 

Q. What is the second planet? 

A. Venus. 

Q. Where is it situated ? 

A. Between the orbits of Mercury and the 
Earth. 

Although Venus is 
one of the nearest 
planets to the Earth, 
astronomers have ex- 
perienced great diffi- 
culty in measuring its 
apparent diameter in 
a precise manner. 
This is owing to the 
astonishing brilliancy 
of the light of Venus, ~~ FlG ]6 " ~~ her day 

and to the irradiation Apparent dimensions of Venus at its extreme and mean distance from the Earth. Q What is the rate 

which is produced in its image in our instru- I of motion in her revolution around the Sun ? 
ments. A. Seventy-seven thousand miles an hour. 

Q. How far is it from ■ 5 / • Eg ^tJSSS^^ SBi Q- What is the inclina- 

the Sun ? t* ^.-s^^^M^ ^ 0I " ner ax i 8 to the 

A. Sixty-eight million I ^^r ^^B ~- ? \ : fl plane of her orbit? 

miles. Ha ^Sf L .J^m BS -A-- Ninety degrees. 

Q. How long does it I K| 4. i : B 19 ^' For wliat is Venus 

take Venus to make a I Hf ®* jfl . ^■distinguished? 

revolution around the I B^^-^-^fl " JSSBi A. She is the most bril- 

Sun? ^Sfe^jad lKg WBB liant planet of all the 

A. Two hundred and I ' - reSsf *»'*-- ?*rM orbs except the Sun and 



Revolution — Indication — Inclination of Orbit with Ecliptic — 
Inclination of Axis with Plane of Orbit — How Distinguished. 

Q. What does this indicate ? 
A. The length of its year. 
Q. What angle does the inclination of her orbit 
make with the Ecliptic ? 
A. Three degrees, twenty-three minutes and 
thirty-three seconds. 

Q. How long does 
it take Venus to turn 
on its axis ? 

A. Twenty- three 
hours and twenty 
minutes. 

Q. What does this 
determine ? 
A. The length of 




twenty-five days. 



Comparative dimensions of Venus and the Earth. 



Moon. 



LESSON XVIII. 

Analysis. — Satellite — Venus and Mercury Satellites of the Sun — Evidence — How Discovered — What Names — Diameter — Ap- 
pearance — Similarity to Moon — Conjunctions — Appearance in Each. 



Mercury and Venus Satellites of the Sun. 
Q. What is a Satellite ? 
A. An attendant body of a primary planet. 



Q. What evidences have we that Mercury and 
Venus are satellites of the Sun ? 



PLATE VI. 




WEED. PARSONS & C?.ALBANY. 



A.TOLLE.PHOTD. LITH 



FORM AND SURFACE MARKINGS OF VENUS 



ELECTRO-ASTRONOMICAL ATLAS. 



31 



A. Their close proximity to the Sun, and the 
uniformity of their movements and appear- 
ance. 

Q. How can we now easily discover this planet 
Venus ? 

A. Because it is the largest and brightest of the 
stars. 

Evening and Morning Star. 

Q. By what name is Venus familiarly known ? 

A. Evening and Morning Star. 

Q. Why? 

A. Because for some months of the year she is 
found brilliantly shining in the west just after 
sunset, as the "Evening Star." She then gradu- 
ally approaches the Sun, and for a time dis- 
appears, but soon reappears in the east in all her 
splendor, just before the rising Sun, as the 
"Morning Star." 

Q. What is the diameter of Venus ? 

A. Seven thousand eight hundred miles. 



Q. What is her appearance when seen through 
a telescope at different times ? 

A. All the different phases are manifest which 
we behold in the moon. 

Q. Is Venus an interior or exterior planet ? 

A. Interior. 

Q. Why? 

A. Because she revolves within the orbit of the 
Earth, or between the Earth and the San. 

Q. How many conjunctions have Venus ? 

A. Two — superior and inferior. 

Q. When in superior conjunction ? 

A. When situated beyond the Sun and in 
range with it and the Earth. 

Q. When is she in her inferior conjunction ? 

A. When between the Earth and the Sun, and 
in range with it. 

Q. What is the appearance of the planet when 
in superior conjunction ? 

A. It is then full like our full moon. 



LESSON XIX. 



Analysts. — Venus — Different Changes — Diameter — Difference 
in Transit — Time of Transits — Time of Last One — Occur 
Century — How far Recede from Sun. 

Changes of Venus. 

Q. What change then occurs ? 

A. It gradually diminishes until, at the time 
of its great elongation, 
only half of the disc is 
seen, then the planet 
continues to wane, un- 
til near its inferior con- 
junction it assumes the 
form of a slender cres- 
cent. 



-^. RET 



Fig. 
The Variatioi 



in Size — Transit — Time When — Benefit Derived — Appearance 
When— Time of Last — When Next — Peculiarity of Twentieth 

Q. Why is the apparent diameter least when 
the planet is full ? 
A. Because it is then farthest from the Earth ? 
Q. When is it greater 
than at any other time ? 
A. It is always great- 
er when near an infe- 
rior conjunction than at 
any other time, except 
when it is seen during 
her transit. 

Q. What is meant by 
her transit ? 



llillll 

W *Z&> DIRECT w ' W 



0£ SSS^^-X f^\ ^- 



32 



ELECTRO-ASTRONOMICAL ATLAS. 



A. Her passage across the disc of the Sun. 

Q. Why does it not occur at every inferior 
conjunction ? 

A. Because one-half of this planet's orbit is 
three and one-half degrees below the plane of the 
Earth' s orbit, and the other half as many degrees 
above it. 

Q. What benefits have been derived from in- 
vestigating the transits of Yenus ? 

A. Owing to the minute investigations of them, 
the distance of the Sun and the dimensions of the 
planetary system have been more cleary deter- 
mined. 

Q. How long do some of these transits last ? 

A. Nearly seven hours. 

Q. What is her appearance in a transit ? 

A. That of a dark spot. 

Q. When did her last transit take place ? 



A. In the year 1769. 

Q. Are these transits of frequent occurrence t 

A. They are very rare, taking place at intervals 
of about eight and one hundred and thirteen 
years. 

Q. When will the next transit transpire ? 

A. December 8th, 1874. 

Q. At what time will the next occur 1 

A. December 6th, 1882. 

Q. What peculiar fact respecting the transit 
of Venus during the twentieth century ? 

A. There will be no transit in that century. 

Q. When will there be another transit of 
Venus ? 

A. June 7th, 2004. 

Q. How far does Venus recede from the Sun 
when in its extreme elongation ? 

A. Forty-seven degrees. 



LESSON XX. 

Analysis. — Mountains of Venus — Height — Schroeter's Statement — Volume — Light Compared to that of the Earth — Distance 
from the Earth — In Different Conjunctions — Circumference of Orbit — Phases — Evidence of What — How Change her Ap- 
pearance. 



Mountains of Venus. 

Q. What is known of the Mountains of Venus ? 

A. Schroeter states that the Mountains of 
Venus are twenty-seven miles high, or five times 
the height of the loftiest peak on the Earth. 

The solid ground of Venus is uneven, like that 
of Mercury and of the Earth ; it is covered with 
high mountains. But is it certain that these as- 
perities attain such a considerable height as is 
stated ? Do mountains exist on Venus to the ver- 
tical elevation of twenty-seven miles ; that is to 
say, five times higher than the most elevated 
peak in Thibet, ten times the colossal Mont 
Blanc 1 This is a delicate question which 



quent measurement may perhaps settle. But if 
the first results were confirmed, we could scarcely 
help thinking of the strange aspect the mountain- 
ous regions of Venus would offer ; the sublime 
peaks of our Alpine regions would be but mere 
mole-hills in comparison. If we refer to the 
drawings of Schroeter (see plate V.), which repre- 
sents Venus in three of its phases, we shall notice 
that the luminous part of the disc is far from ter- 
minating abruptly along the line of shade. Its 
light, on the contrary, diminishes gradually ; and 
this diminution may be entirely explained by the 
twilight on the planet. 
Q. What is said of its volume ? 



PLATE VII 




WEED. PARSONS &CO.,ALBANY.N.Y. 



A TDLLE.PHOTO-LITH. 



THE EARTH SUSPENDED IN SPACE 



ELECTRO-ASTRONOMICAL ATLAS. 33 


A. It is a little less than that of the Earth. 


A. That she passes through all the motions 


Q. How does the quantity of light compare 


and phases of an Evening and Morning Star. 


with that of the Earth ? 


Q. What does this prove ? 


A. It is about twice as great. 


A. That the Sun is in the center of the Solar 


Q. How far is Venus from the Earth when in 


System, and that the Earth, on which we live, is 


her inferior conjunction ? 


revolving around it in an orbit more distant than 


A. Twenty-seven million miles. 


Venus. 


Q. How far is her superior conjunction ? 


Q. Were the enlightened hemisphere of Venus 


A. One hundred and sixty-three million miles. 


turned toward the Earth, when in that point of 


Q. What is the circumference of her orbit % 


the orbit nearest to us, how would she appear ? 


A. Five hundred and thirty-three million eight 


A. Like a brilliant moon, twenty -Ave times 


hundred thousand miles. 


larger than she now appears to the naked eye. 


Q. What length of time intervenes between one 


Q. Why does she not appear so to us % 


conjunction and another ? 


A. Because at that time her light side is turned 


A. Five hundred and eighty-four days. 


toward the Sun, and her dark side toward the 


Q. During this time what may be observed of 


Earth. 


her? 




LESSON XXI. 


Analysis. — The Earth — Situation — Form — Spherical — Evidence — Not Perfect — Proved — Difference of Diameter — Position 


Important. 


The Earth. 


In explanation of the following figures, let us 


Q. What is the Earth % 


dwell a short time on their different points. 


A. An opaque body ; the third planet in the 


It is well known that the horizon of a plain 


order of distance from 




presents the form of a 


the Sun? 


^=-^^-^-:^==r 


circle surrounding the 


Q. What is its form \ 


'- == - 


observer. If the latter 


A. That of an oblate 


"^ 


moves, the circle moves 


spheroid, approaching 


■ : - ^=-^jl:.L'..' ..:■■"■'" ' '■ "'-"' =H 


also, but its form re- 


nearly to the form of a 


~^^^ikWMm^=^^~ c :■': "■'""" - iHHl 


mains the same, and is 


globe. 


:: ; ^itS^?; :■■■■/-■■-: -p^= 


modified only when 


Q. What is an oblate 


^ ^2^£0 i ^_ i ^^J ! I^^^^ : '~^^p- 


mountains or other ob- 


spheroid % 


-- \ ^^^""/-nn j "heicjT}i-^-^ / "~^- 


stacles of some eleva- 


A. A sphere flattened 


^^^ X ^-=2l_iV/ the r^!LJ-^ / 


tion limit the view. Out 


at two points opposite 


^^^i«f m _^^~^ 


at sea, the circular form 


each other, called the 


a s — 


of the horizon is still 


Doles Fl&> 19 - 

F ulco - A Mountain figured on a Plain. 


more decided (fig. 19 ) } 



34 



ELECTRO-ASTRONOMICAL ATLAS. 



and changes only near the coasts, the outline of 
which breaks the regularity. 

Here, then, we obtain the first notion of the ro- 
tundity of the earth, since a sphere is the only 
body which is always presented to us under the 
form of a circle, from whatever exterior point of 
view it is examined. Moreover, it cannot be said 
that the horizon is formed by the limit of distinct 
vision, and that it is this which causes the appear- 
ance of a circular boundary, because the horizon 
is enlarged when we mount vertically above the 
surface of the plain. 
The preceding draw- jS' 

ing, in which a moun- MSjk' 
tain is figured in the 
middle of a plain, 
whose uniform cur- 
vature is that of a 
sphere, will prove our 
assertion. From the 
foot of the mountain 
the spectator will 
have but a very lim- 
ited horizon. Let him 
ascend half-way, his 
visual radius extends, 
is inclined below the 
horizon, and reveals 
a more extended cir- 
cular area. At the summit of the mountain the 
horizon increases, and if the atmosphere be pure, 
the spectator will see numerous objects appear ; 
where, from the lower stations, the sky alone was 
visible. 



This extension of the horizon would be inexplic- 
able if the Earth had the form of an extensive 
plain. The curvature of the surface of the sea 
manifests itself in a still more striking manner. 
Suppose yourself on the coast, at the summit of a 
high tower, hill or steep, rocky shore ; a vessel 
appears on the horizon, you see only the tops of 
the masts — the highest sails; the lowest sails 
and the "bull are invisible ; as the vessel ap- 
proaches, its lower part comes into view above 
the horizon, and soon it appears entire. (Fig. 20.) 
The fact of the suc- 
cessive appearances 
on the surface of the 
sea, or the different 
of an object, 





beginning by the 
highest parts of it, is 
manifested in the 
same manner to the 
sailors who, from the 
ship , observe the 
land. The explana- 
tion is rendered clear 
in the following 
sketch, where the 
course of a vessel, 
seen in profile, is fig- 
ured on the convex 

surface of the sea. (See fig. 21.) 
As the curvature of the ocean is the same in 

every direction, it follows that the earth has really 

the form of a sphere, or at least differs from it but 

little. 



Fig. 21. 
A Vessel figured on the Convex of the Sea. 



ELECTRO-ASTRONOMICAL ATLAS. 



35 



Q. How do we know the Earth is spherical ? 

A. By the sailing of a ship around it. 

Q. Who first sailed around the Earth ? 

A. A Portuguese by the name of Ferdinand 
Magellan. 

Q. Who next made the voyage ? 

A. Sir Francis Drake. 

Q. In what year and from whence did he sail? 

A. He sailed from Plymouth, December 13, 
1577, with five small vessels, and arrived at the 
same place from whence he started September 26, 
1580. 

Q. Since that time has the Earth been circum- 
navigated ? 

A. By many others ; among them Cavendish 
and Cordes. 

Q. In what direction did they sail ? 

A. In a westerly direction. 

Q. What other proof have we that the Earth is 
nearly round ? 

A. The shadow of the Earth in the eclipse of 
the Moon indicates a globular figure. 



Q. Is the Earth a perfect sphere ? 

A. It is not. 

Q. How is this known ? 

A. By actual measurement. The degrees from 
the equator to the poles are not uniformly the 
same ; but increase in length with the latitude, as 
we go from the equator to the poles, thus show- 
ing the Earth is not a true sphere or globe. 

Q. What is the longest or equatorial diameter?. 

A. Seven thousand nine hundred and twenty- 
four miles. 

Q. What is the polar diameter ? 

A. Seven thousand eight hundred and ninety- 
eight miles. 

Q. What is the mean diameter ? 

A. Seven thousand nine hundred and twelve 
miles, and their difference twenty- six miles. 

Note. — The Earth, considered as a planet, holds a very im- 
portant and conspicuous position in the solar system. It has 
pleased an infinitely wise Creator to assign its positions among 
the heavenly bodies, where nearly all of them are visible to the 
naked eye. 



LESSON XXII. 

Analysis. — Eevolution of the Earth — Time — Indication — Changes of Seasons — Axis — Position — Time of Revolution on 
Axis — Production — Cause of its Eevolution on its Axis — Explanation — Illustration — Law Equally Essential in all Planets — 
Problem Solved — Distance from Sun — Circumference of Orbit — Rate of Motion — Inclination of Axis. 



Revolution of the Earth. 

Q. How long does it take the Earth to revolve 
around the Sun ? 

A. It moves around the Sun from west to 
east in 365 days, 5 hours, 48 minutes and 48 
seconds. 

Q. What is this called ? 

A. Her year, or annual motion. 

Q. What does this annual motion produce ? 

A. The changes of seasons. 



Q. What is the axis of the Earth ? 

A. An imaginary line passing through the 
center of the Earth and terminating at the poles. 

Q. What is the position of its axis ? 

A. It is always parallel to itself, pointing in 
the same direction in the heavens. 

Q. How often does the Earth turn on its axis ? 

A. Once in every 24 hours. 

Q. What is this called ? 

A. Her diurnal motion, or her day. 



36 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. Wiiat does this revolution produce % 
A. The succession of day and night. 

In view of the fact, admitted by all, that God created the 
planets, and sent them rolling in their respective orbits, we 
come to the conclusion that He has constituted a certain law by 
which they are continued in motion ; hence, we present the hy- 
pothesis that they are continued in their revolutions by the elec- 
trical law of Attraction and Repulsion. 

We call attention now to the following explan- 
ation of this law, and humbly ask of the Scientific 
World to present another more feasible one, and 
in which the controlling power of the Sun can be 
illustrated by attraction and repulsion. 

Q. What law continues the revolution of the 
Earth on its axis ? 

A. The immutable law of Electricity, manifest 
in attraction and repulsion. 

Q. How is that law explained ? 

A. Two positives repel each other, and a, posi- 
tive and a negative attract each other. 

Q. How is this law illustrated in the continued 
revolution of the Earth ? 

A. That part of the Earth which has been long- 
est in the rays of the Sun having become positive, 
by the electrical influence of the Sun, is repelled. 
The opposite portion of the Earth, lying in the 



dark, and thus becoming deeply negative, is at- 
tracted by the positive Sun ; hence, the revolution 
of the Earth is continued. 

Q. Is this law simply applicable to the revolu- 
tion of the Earth on its axis ? 

A. Certainly not. It is equally essential to the 
revolution of every planet in the Solar System. 

Q. In applying this law to the revolution of the 
planets, what problem is solved which hitherto 
has remained a mystery % 

A. The cause of attraction and repulsion. 

Q. How far is the Earth from the Sun ? 

A. When the Earth is in aphelion, the distance 
is ninety-three million miles ; when in perihelion, 
it is ninety million miles, the mean distance being 
ninety-one and one-half million miles. 

Q. What is the circumference of the Earth's 
orbit % 

A. It is six hundred million miles. 

Q. What is the rate of the Earth' s motion ? 

A. It is sixty-eight thousand miles an hour. 

Q. What is the inclination of the axis of the 
Earth? 

A. It is twenty-three and a half degrees from a 
perpendicular to the plane of the Earth's orbit. 



LESSON XXIII. 



Analysis. — Time — How Reckoned — Uniformity — Advantage Derived — Remarks — Plane of Eclipti 
Law — Location of Sun in Earth's Orbit — Shape of Orbit. 



Illufltrated — Kepler s 



How Time is Reckoned. 

Q. Is the rotation of the Earth on its axis 
always uniform and invariable ? 

A. Its revolution is invariably the same, once in 
twenty-four hours. 

Q. What advantage is derived from this regu- 
larity of the Earth' s motion ? 



A. We obtain by this the only true principle 
of reckoning time in hours, days, etc. 

Remark. — 1st. While all the other periodical 
motions of the heavenly bodies are subject to 
change, this has remained the uniform standard, 
having undergone not the slightest appreciable 
change from the date of the earliest observation. 



ELECTRO-ASTRONOMICAL ATLAS. 



87 



2d. The different periods of time in common use 
all date from this. Weeks, months and years are 
recorded by days and fractions of a day ; while 
hours, minutes and seconds are divisions and 
subdivisions of the day. 

Q. How may we illustrate the plane of the 
Ecliptic ? 

A. By filling a bowl with water, the rim will 
represent the orbit, the surface of the water even 
with the rim of the bowl, the plane of the Eclip- 
tic, and the bowl would represent one-half of the 
concave sky. 



Q. What law of Kepler respecting the planets, 
by which the primary and secondary are regu- 
lated, and to which law there is no exception 
known ? 

A. That the square of the periodic times of the 
planets' revolution is as the cubes of their dis- 
tances. 

Q. How far is the Sun one side of the center of 
the orbit in which the Earth moves around it % 

A. It is about three million miles. 

Q. What is the shape of the Earth's orbit ? 

A. It is that of an ellipse. 



LESSON XXIV, 



Analysis. — Causes of their Change — How far is the Axis of Rotation Inclined to Plane of Ecliptic — Time of Tear— Equal Day 
and Night — Why Then— Why Day — Why Night — The Result of the Revolution of the Earth on its Axis — Points Called 
— Way of the Revolution. 



The Seasons. 

Q. What causes the change of the seasons ? 

A. First, the fact that the Sun illuminates but 
one-half of the Earth at a time ; secondly, that 
the axis on which the Earth revolves is inclined 
to the plane of the Ecliptic ; thirdly, that its posi- 
tion at any one point in the Earth's orbit is 
invariably parallel to its position at every other 
point. 

Q. How far is the axis of rotation inclined to 
the plane of the Ecliptic ? 

A. About sixty-seven and a half degrees. 

Q. At what time of the year do we have equal 
day and night % 

A. On the 21st of March and on the 23d of Sep- 
tember. 

Q. Why do we have equal day and night at 
that time \ 



A. The Sun at those points strikes us vertically 
at the equator and shines from pole to pole. 

Q. What is the side of the Earth toward the 
Sun called % 

A. It is called Day. 

Q. What is the side turned from the Sun called % 

A. It is called Night. 

Q. What is the result of the revolution of the 
Earth on its axis % 

A. Where it was day it becomes night, and 
where it was night it becomes day, and the day 
and night are equal. 

Q. What are those points called % 

A. Equinoctial points. 

Q. Which way does the Earth move around 
the Sun 1 

A. From west to east. 



N. B. — The teacher will 
the first part of the Atlas. 



explain this on the Diagram in 



38 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON XXV. 



Difference of Time in the Days and Nights Explained - 
Beyond the North Pole — Situation of South Pole - 



Summer Solstice — Why so Called — Distance the Sun Shines 
- Movements of the Sun Further Explained. 



The following instruction should be illustrated by the teacher 
on the Diagram : 

Q. Why do the days grow longer and the 
nights shorter from the 20th of March until the 
21st of June ? 

A. Owing to the inclination of the Earth's axis 
as the Earth moves along in her orbit from her 
place in March, more and more of the northern 
hemisphere is coming into the light of the Sun ; 
and the Sun shines farther and farther beyond 
the North Pole until the 21st of June, hence the 
Earth turning on its axis ; in the meantime, the 
days continue to increase till then, and nights 
grow shorter in the same proportion. 

Q. Why is the 21st of June the longest day in 
the year ? 

A. The most of the northern hemisphere is en- 
lightened that can be at any one time. 

Q. What is this point called ? 

A. The summer solstice. 

Q. Why is it so called ? 

A. The Sun then has its greatest northern 
declination, or is at its greatest distance north of 
the equinoctial line, or the equator. 

Q. How far does the Sun then shine beyond 
the North Pole J 

A. It shines twenty-three and a half degrees. 

Q. What is the situation of the South Pole at 
this time ? 



A. It is entirely in the dark. 

Q. What takes place when the Sun reaches the 
summer solstice ? 

A. It then ceases to decline from the equinoc- 
tial, and begins to return toward it. 

Q. How is this accomplished ? 

A. By the Earth moving along in her orbit, the 
North Polar circle advances farther and farther 
into the dark, and the South Polar circle in a cor- 
responding manner extends into the light until 
the 22d of September, when the Sun again strikes 
vertically at the equator and shines from pole to 
pole, causing once more equal day and night. 

Q. Why do the days grow shorter and the 
nights longer from the 22d of September till the 
21st of December ? 

A. The axis of the Earth being inclined always 
in the same direction, as the Earth moves along 
from west to east in her orbit, the North Polar 
circle recedes farther into the dark, and the South 
Polar circle advances more and more into the 
light, so that less of the northern hemisphere is 
enlightened by the Sun, and more of the southern 
until the 21st of December the Sun has reached 
its greatest southern declination, or is at its great- 
est distance south of the equinoctial, when the 
winter solstice is reached, and when the Ecliptic 
and the Equator are at their greatest distance 
from each other. 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON XXVI. 

Analysis. — Length of the Days and Nights Considered — Number of Seasons — What Called — Zodiacal Light — Time of Ap- 
pearance — In what Part of the Heavens — Form of the Light — Compared with Milky Way — Not Seen at all Seasons — When 
Only — In what Months — Favorable Nights — Zodiac — What is it — Description of Belt — How Occupied — Location of Eclip- 
tic — Term "Constellation" — By Whom Used — Why Called Zodiac — What Use is made of the Signs of the Zodiac — Names 

Correspondents of these — The Earth in Capricorn — Where then is the Sun Vertical ? 



Q. What may be said of the days and nights 
at this time % 

A. The days are the shortest and the nights the 
longest of any time during the year. 

Q. As the Earth continues on in her course, 
what effect is produced % 

A. The days grow longer and the nights shorter 
until they become equal again, on the 21st of 
March. 

Q. How many seasons have we % 

A. Four. 

Q. What are they called % 

A. Spring, Summer, Autumn and Winter. 

The Zodiacal Light. 
In the evenings, about the time of the vernal 
Equinox, — in March and April, — when in our 




Pig. 22. 
Direction of the Axis of the Zodiacal Light. 



climate the twilight is of short duration, if we 
examine the horizon toward the west a little after 
sunset, we may perceive a faint light that rises in 
the form of a cone among the starry constella- 
tions. This is what astronomers call the Zodi- 
acal Light. 

Let us see now if it is possible to account for the 
nature of the Zodiacal Light, which evidently is 
not a purely meteorological phenomenon, since 
its participation in the diurnal movement, its 
visibility in regions of the Earth very distant one 
from the other, and, lastly, its nearly invariable 
inclination along the Ecliptic, indicate sufficiently 
that the cause which produces such appearances 
lies outside our atmosphere, in the celestial 
spaces. 

Among the explanations that have been given, 
the most probable one is that which likens the 
Zodiacal Light to a flattened nebulous ring sur- 
rounding the Sun at some distance. It is to be 
remarked, that the direction of the axis of the 
cone, or of the pyramid, prolonged below the 
horizon, always passes through the Sun. (See 
Pig. 22.) 

It was believed at first that this direction pre- 
cisely coincided with the solar equator; but it 
seems more certain that it coincides with the 
plane of the Earth' s orbit, or the Ecliptic. 

Another hypothesis, also connected with the 
first is that the Zodiacal Light is formed from 
myriads of solid particles analogous to the aero- 
lites, possessing a general movement but traveling 
separately around the focus of our solar 
world. 



40 



ELECTRO-ASTRONOMICAL ATLAS. 



The light of the ring would be thus produced 
by the accumulation of this multitude of brilliant 
points reflecting toward us the light borrowed by 
each of them from the Sun. This explanation 
accounts for the variation of the intensity of the 
Zodiacal Light at different epochs ; it would suffice 
to admit that the condensation of the particles or 
the density of the ring is not the same throughout 
its extent, and its movement of its circulation 
round the Sun presents, successively, different 
parts to the Earth. In this case, it becomes a 
question whether this lenticular ring of matter is 
distinct from the systems of meteors, of which we 
shall hereafter speak, and the existence of which 
seems at length established. 

Q. In what season of the year does the light 
make its appearance ? 

A. In March and April ; in the evenings, about 
the time of the Vernal Equinox. 

Q. In what part of the heavens does it appear ? 

A. It is seen in the west, near the place where 
the Sun sets. 

Q. What is its form and appearance ? 

A. It extends upward in the form of a cone, 
and is brighter in appearance than the Milky 
Way. 

Q. Why is it not seen at all seasons of the 
year? 

A. It is only seen when our twilight is of short 
duration ; when it increases the Zodiacal Light 
disappears. 

Q. Is it not seen at any other time of the day, 
or of the year ? 

A. It may be seen about the time of the Autum- 
nal Equinox, in the months of September and 
October, in the morning, when the dawn has an 
equally short duration. 

Q. When is it most favorable to take a view of 
it? 

A. When the night is clear and the night is 
moonless. 



Zodiac. 

Q. What is the Zodiac ? 

A. It is an imaginary belt, 16 degrees in width 
surrounding the heavens from west to east. 

Q. What does this Belt show ? 

A. The width of space occupied by the planets 
of our solar system in revolving around the Sun. 

Q. What part of this space is occupied by the 
Ecliptic ? 

A. The center ; hence eight degrees lie on one 
side and eight on the other of the orbit. 

Q. Who first applied the term " constellation" 
to that portion of the heavens embraced in the 
Zodiac ? 

A. The Chaldeans or Egyptians. 

Q. Why was it called Zodiac ? 

A. From the Greek word "Zoon," which means 
an animal. 

Q. What did the Chaldeans imagine ? 

A. That many animals and objects were repre.- 
sented in the heavens. 

Q. How many are the signs of the Zodiac ? 

A. There are twelve. (See plate of the Seasons.) 

Q. To what purpose did the signs of the Zo- 
diac serve the ancients ? 

A. That of Calendar, enabling them to tell 
when to plant and sow their grain. 

Q. What names were given to the constellations 
forming the Zodiac ? 

A. Aries, Taurus, Gemini, Cancer, Leo, Virgo, 
Lebra, Scorpio, Sagittarius, Capricornus, Aquar- 
ius, and Pices. (Refer to plate above.) 

Q. To what do these constellations correspond ? 
(See plate of the Seasons.) 

A. To the twelve months of the year, begin- 
ning at September, letting it be represented by 
Aries, October by Taurus, and so on. 

Q. When the Earth is in that constellation 
called Capricorn, where js the Sun then vertical ? 

A. To the constellation in the heavens directly 
opposite at Cancer. 



ELECTRO-ASTRONOMICAL ATLAS. 



41 



LESSON XXVII. 

Analysis. — What Does This Show — Why Warmer on the 21st of June — Sun Further Away — Difference in Diameter — Difference 
of Time in Equinoctial Points — Nearest the Sun Perihelion — Fartherest Aphelion — Motion Faster at Which — Density — 
Variation of Equinoctial Points — Difference of Diameter — Discovery — Weight at the Poles and the Equator — Cause of This. 



Q. What does this show ? 

A. That when it is Summer with us in the Nor- 
thern Hemisphere, that is in June, in the constel- 
lation Capricorn, and the Earth passes in its orbit 
to the direct opposite point in the constellation 
Cancer, which is December, the inhabitants will 
have then the same season of the year, south of 
the Equator, that we had in June north of the 
Equator, and so at every opposite point of the 
Earth's orbit. 

Q. Why is it warmer with us, north of the 
Equator, on the 21st of June, when we are three 
millions of miles further from the Sun than on 
the 21st of December? 

A. The Sun rises to a much higher altitude 
above the horizon in Summer than in Winter, 
hence, its rays fall more directly and less ob- 
liquely npon the surface of the Earth. 

Q. What is the difference of the length between 
the longer and the shorter diameter of the Earth' s 
orbit 1 

A. It is three millions two hundred and thirty- 
six thousand miles. 

Q. How is this ascertained % 

A. From the variation of the apparent diameter 
of the Sun. 

Q. What is the difference of time between the 
Equinoctial points ? 

A. There are between seven and eight days 
more between the 21st of March to the 23d of 
September than from the 23d of September on- 
ward to the 2lst of March. 

Q. What is that point called when the Earth is 
nearest the Sun % 

A. It is called Perihelion distance % 

Q. What is that point of its greatest distance 
called % 

A. It is called Aphelion. 



Q. Does the Earth move faster at its Perihelion 
than its Aphelion distance % 

A. It moves more than three thousand miles an 
hour faster. 

Q. What is the density of the Earth ? 

A. About five times that of Water. 

Q. What is known in regard to the varying of 
the Equinoctial points ? 

A. They are slowly receding or falling back 
westward on the Ecliptic. 

Q. How is this caused ? 

A. The Earth, in passing around the Sun, 
reaches the Equinoctial points twenty-two min- 
utes and twenty-three and a half seconds earlier 
each year, and in the course of twentj^-five 
thousand eight hundred and sixty-eight years 
they will perform a retrograde motion quite 
around the heavens. 

Q. What is the difference between the length of 
the Equatorial and the Polar diameters of the 
Earth % 

A. The Equatorial diameter is about thirty -four 
miles the longer. 

Q. What trifling circumstance led to this impor- 
tant discovery 1 

A. The difference of the number of the vibra- 
tions of a pendulum of the same length makes in 
different latitudes ; also that a body or substance 
weighing 194 pounds at the Equator would weigh 
195 pounds at the poles. 

Q. What is the cause of a body weighing more 
at the Poles than at the Equator ? 

A. The motion of the Earth's surface is not so 
great as at the Equator, and it is nearer the cen- 
ter of the Earth, hence, the body would not have 
so great a tendency to fly off, and, being nearer 
the center of the Earth, is attracted toward it with 
more force. 



42 



ELECTRO-ASTRONOMICAL ATLAS. 



A. There is no difference in time. 

Q. Then how many lunar days make a year ? 

A. It takes thirteen days. 




LESSON XXVIII. 

Analysis. — The Moon — Form of Orbit — Perigee — Apogee — Mean Distance — Inclination of its Orbit to Plane of Ecliptic — 
Lunar Days in a Year — How muck of Moon Seen — Illustrated — Evidence of any Life on the Moon — Result if there were — 
Any Seas, Lakes, Rivers — Any Winds or Tornadoes. 

The Moon. 

Q. How many Satellites has the Earth ? 

A. The Earth has one Satellite, called the 
Moon. 

Q. How far is it from the Earth ? 

A. It is two hundred and forty thousand miles. 

Q. How long does it take this Satellite to re- 
volve around the Earth % 

A. It takes 27 days, 7 hours and 43 minutes 
and 11^ seconds from one fixed star to the same 
fixed star again. 

Q. What is the form of its orbit ? 

A. It is Elliptical. 

The Teacher in giving the instruction of the Moon should fre- 
quently refer to the Diagram in the front part of the Atlas. 

Perigee and Apogee. 

Q. What is the point nearest the Earth called % 

A. It is called the Perigee. 

Q. What is the point farthest from the Earth 
called % 

A. It is called the Apogee. 

Q. What is its mean distance from the Earth % 

A. It is two hundred and thirty-eight thousand 
eight hundred miles. 

Q. How much nearer to us in Perigee than in 
Apogee % 

A. It is twenty- six thousand miles. 

Q. What is the inclination of the Moon's orbit 
to the plane of the Ecliptic % 

A. It is five degrees and eight minutes. 

Q. What is the diameter of the Moon ? 

A. It is two thousand and one hundred and 
sixty miles. 

Q. What is the difference between a lunar day 
and a month upon the earth % 



Comparative Dimensions of the Earth and Moon. 

Q. How much of the Moon do we see ? 

A. Only one side is ever seen ; that being turned 
toward us when seen. 

Q. How may this be illustrated % 

A. Let a person walk around an object, keep- 
ing his face toward it all the time, and he will 
beautifully illustrate the manner the Moon always 
turns her face toward and goes around the Earth. 

Remark. — Here the teacher should turn the attention of the 
class to the diagram in the first part of the Atlas. 

Q. Have we any evidence that there is animal 
or vegetable life on the Moon % 

A. None whatever ; no moving object has ever 
been seen on the disc of the Moon. 

Q. Is there any evidence that there are seas, 
lakes, or rivers on the Moon % 

A. If there were, the solar heat would develop 
a gaseous envelope, and thick clouds of vapor, 
which have never been discovered. 

Q. Are there winds or tornadoes manifest over 
the surface of the Moon \ 

A. There being no water, of necessity there is 
an absence of winds, currents, or even air itself. 



PLATE X 




-A.TOLLE, photo-lith. 



ORBIT OF THE MOON 

EXPLANATION OF THE PHASES. 



ELECTRO-ASTRONOMICAL ATLAS. 



43 



LESSON XXIX. 

Analysis. — Phases of the Moon — Explanation of them — First Appearance where — At what time — Way of Revolution — 
Degrees in twenty -four hours — Her Changes Explained — Time of Pull Moon — Position now in Respect to Sun — Why in 
Opposition. 

Phases op the Moon. 

Q. What is understood by the Phases of the 
Moon? 

A. They are different illuminated aspects she 
presents in her revolution around the Earth. 

Q. In her revolution, what is her first appear- 
ance? 

A. She appears in the form of a beautiful 
crescent, with horns turned toward the east. 

Q. In what part of the heavens and at what 
time does she appear in this form ? 

A. She may be seen in the west just after sunset. 

Q. Which way does she revolve around the 
Earth ? 

A. Prom west to east. 

Q. How many degrees eastward does she pass 
in twenty-four hours ? 

A. She passes thirteen degrees, ten minutes, 
and thirty -five seconds. 



Q. What changes take place in her luminous 
appearance from evening to evening, as she con- 
tinues her revolution ? 

A. As she departs further and further from 
the Sun, her enlightened surface comes more and 
more into view. 

Q. How many degrees does she pass in reach- 
ing her first quarter ? 

A. She passes just ninety degrees. 

Q. What is her appearance at this point ? 

A. Having finished just half of her course 
from the new to the full Moon, she presents just 
one-half of her enlightened hemisphere toward 
the Earth. 

Q. What changes mark her appearance as she 
continues her course ? 

A. She constantly increases her luminous ap- 
pearance, presenting a gibbous face to the Earth. 




Kg 
Kotation of a Sphere, 

We must recollect that it is the phases of the 
Moon which have demonstrated to us its revolu- 
tion round the Earth. This movement, added to 
the fact that the Moon constantly presents the 
same hemisphere to the Earth, proves that it turns 
also on itself, in a period of time exactly equal 
to the length of its sidereal revolution, that is to 
say, in about twenty-seven days and a third. 

In speaking of the movement of rotation of 



the Moon on its axis, it is right to anticipate an 
objection often made, proceeding from a false idea 
sometimes conceived of the rotatory movement 
of a movable body. "Since the Moon," it is 
said, "always presents the same face to us, it 
cannot turn on itself. If it turned on an axis or 
pivot, it ought to present us all its sides succes- 
sively." Such is the objection simply put. 
To solve this difficulty, let us examine into the 



44 



ELECTRO-ASTRONOMICAL ATLAS. 



phenomena. What is a movement of rotation ? 
How is it known that a body, a sphere for exam- 
ple, does rotate ? and how is it known when an 
entire rotation has been completed ? Evidently, 
when the sphere has presented successively one 
of its sides toward every point of the space 
which surrounds it. If we divide the entire ro- 
tation into four periods, the accompanying dia- 
gram -will show how the sphere would be seen 
at the commencement of each of those periods, 
to an observer at rest. 

Now, if the sphere, during the exact time that 
it takes to effect this rotation round its axis, exe- 
cutes a movement of revolution round the obser- 
ver, whether the observer be at rest or not, it is 
none the less evident that the entire rotation would 
be effected, * if the side, of which the point A 
forms the apparent center, is successively pre- 
sented to all parts of space. Now, this is the 
case with the Moon, during a complete revolution 
in its orbit, as may be seen from the comparison 
of figures 24 and 25. 



Q. What changes occur in one lunation of 
the Moon ? 

A. It passes from one Full Moon to another. 

Q. How many times does it cross the orbit of 
the Earth in the course of one lunation ? 




Fig. 25. 
Actual Movement of Rotation of the Moon in the Interval of a Lunation. 

A. It crosses it twice. 

Q. Does it continue to indicate the same posi- 
tion at the end of its rotation as it did at the 
beginning ? 

A. Comparing the indication of the two Full 
Moons with respect to the location of the Earth, 
there is a continued variation during the entire 
rotation. 

Q. Why is there a variation ? 

A. This must necessarily take place in order 
that the same side of the Moon be presented to us 
all times. 

Q. What occurs when she has accomplished 
one-half of her circuit around the Earth % 

A. She appears then as a Full Moon. 

Q. What is now her position, with respect to the 
Sun? 

A. She is in opposition. 

Q. And why in opposition ? 

A. Because she is then on the opposite side of 
the Earth, with respect to the Sun, and is rising 
in the east just as the Sun is setting in the west. 



PLATE XI. 




WEED. PARSONS *CO.,ALBANT,H.Y. 



A.TOLLE..PH0T0-LITH. 



TH E FULL MOON 

(telescopic view.) 



ELECTRO-ASTRONOMICAL ATLAS. 



45 



LESSON XXX. 

Analysis. — Appearance in the First Half of her Orbit — Appearance in the Last Half — What Remarkable in her History - 
When Called New Moon — When Full Moon — Relation to the Earth — Satellite — Time of Revolutions — What Called — Hov 
Near the Earth — Revolutions in a Year — Synodic and Siderial Revolution, 



The Siderial revolu- 
tion of the Moon around 
the Earth is accom- 
plished in about twenty- 
seven and a third days, 
but, owing to the revo- 
lution of the Earth in 
its own orbit around 
the Sun, it takes mor 
than two days longer 
to complete its Synodic 
revolution and come 
into the same position 
as before, with respect 
to the Sun and Earth. 




The wave-like motion 
of the Moon, by which 
it crosses the path of 
the Earth twice each 
month is produced by 
a combination of its 
own peculiar motions 
and the onward move- 
ment of the Earth. As 
the same side of the 
Moon is kept constantly 
toward us, it is evident 
that it must turn on its 
axis once each month. 



Fig. 26. 
described in a year, by the Moon round the Earth. 



Q. In passing over this half of her orbit how 
has her course appeared to us ? 

A. She has apparently passed over our heads 
in the upper hemisphere. 

Q. What change takes place now in her aspect ? 

A. She continues to wane ; rising later on each 
successive evening. 

Q. During her progress through the east half 
of her orbit how does her course appear to us % 

A. She seems to descend below the eastern 
horizon and pass through the lower hemisphere. 

Q. In what form does she next present herself ? 

A. We next behold her in the morning a little 
west of the rising Sun, in the form of a crescent with 
its horns inverted, turned now toward the west. 



Q. What now transpires which is remarkable 
in her history % 

A. She rises and sets in conjunction with the 
Sun and for two or three days we lose sight of her 
altogether. 

Q. By what different terms is she called in the 
first half of her revolution around the Earth ? 

A. When in conjunction, she is called New 
Moon ; having completed her first quarter, Half- 
Moon ; when she is in opposition she is called 
Full Moon. 

Q. What relation does the Moon hold to the 
Earth \ 

A. It is the satellite of the Earth. 



46 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. How long does it take her to revolve around 
the Earth ? 

A. The time from one New Moon to another is 
29 days, 12 hours, 44 minutes and 3 seconds. 

Q. What is this revolution called \ 

A. It is called her Synodic revolution. 

Q. What is her revolution from any fixed star 
to the same fixed star again called 1 



Let S represent the Sun, 
and A the Earth in her orbit. 
When she is at A, a spot is 
seen upon the disc of the Sun 
at B. The Sun revolves in 
the direction of the arrows, 
and in 25 days 10 hours the 
spot comes round to B again, 
or opposite the star E. This 
is a sidereal revolution. 

During these 25 days 8 
hours, the Earth has passed 
on in her orbit some 25°, or 
nearly, to C, which will re- 
quire nearly two days for the 
spot at B to get directly to- 
ward the Earth, as shown at 
D. This last is a synodic 
revolution. It consists of 
one complete revolution of 
the Sun upon his axis, and 
about 27° over. 




KCzsoVwh- 



SIDEREAL AND 



REVOLUTIONS OF THE SUN.! 



A. It is called her Periodic or Siderial revolu- 
tion. 



Q. What time is required to perform this revolu- 
tion? 

A. It requires 27 days, 7 hours, 43 minutes and 
Hi seconds. 

Q. What is the difference between the length of 
a Synodic and a Siderial revolution % 

A. The difference is one day and twenty hours. 

Q. What causes the difference of time % 
A. While the Moon is revolving around the 
Earth, she too is advancing in her orbit. 

Q. Of all the heavenly bodies, which is nearest 
to the Earth % 

A. The Moon is nearest. 

Q. How near is she to the Earth % 

A. She is only two hundred and forty thousand 
miles distant. 

Q. How many revolutions does the Moon per- 
form round the Earth in a year % 

A. Nearly thirteen. 



LESSON XXXI, 



Analysis. — Physical Aspect of the Moon — Appearance Variable — Cause of this — Appearance Through Telescope- 
Mountains — Compared to those of the Earth — Peculiar Formations — Ring Mountains — Description — Eclipses- 
Eclipse — Philosophical Cause Given. 



Rough — 
- Cause of 



Physical Aspects of the Moon. 

Q. Is the Moon uniformly bright in appearance ? 

A. There are alternations of light and shade 
extending over the entire surface. 

Q. What is the cause of this varied appearance ? 

A. These represent lofty and rugged mountains 
and deep valleys. 

Q. How is this demonstrated ? 

A. The Moon, when viewed through a magnified 
telescope, in quadrature, presents on the line of 
light, a shade of a rough and jagged appearance. 



Lunar Mountains. 

Q. What is the appearance of the mountainous 
regions of the Moon when compared with those 
of the Earth % 

A. They equal, if they do not surpass, the rug- 
ged and precipitous ranges of our Globe — travers- 
ing the lunar surface in all directions. 

Q. What peculiar mountain formation does the 
Moon possess ? 

A. They are called Ring mountains. 

Q. How are these formed % 



ELECTRO-ASTRONOMICAL ATLAS. 



47 



A. A deep cavern or crater is often seen on a 
plain, surmounted by a chain of mountains like a 
ring, and, frequently, from the center of this in- 
closed plain an isolated peak shoots up to a 
great height in the sky. 



Ring Mountains. 

Q. How do the mountains differ in appearance 
from other lunar mountains ? 

A. They are lofty mountains, circular in form, 
inclosing a vast area resembling the crater of a 
volcano. 

Q. What is the extent of their diameters? 

A. They are from ten to sixty miles in diameter. 

Q. What other peculiarity in their formation ? 

A. They sometimes contain in their center one 
or more lofty peaks. 

Q. What is observed flowing out from all sides 
of these Ring mountains ? 

A. There are seen streaks of light and shade 
radiating and spreading to a distance of several 
hundred miles. 

Q. What are these called ? 

A. They are called radiating streaks. 

Q. How are they accounted for ? 

A. They are considered by some to be streams 
of lava which have once flowed out in all direc- 
tions from these volcanic mountains. 

Q. For what is Copernicus distinguished % 

A. It is one of the grandest of the Ring moun- 
tains. 

Q. What is the length of its diameter ? 

A. It is fifty- six miles in diameter. 

Q. What is there peculiar in its formation ? 

A. It has a central mountain, two of whose 
peaks are quite conspicuous. 

Q. How high does it rise and what is its form ? 

A. It rises eleven thousand feet, and the sum- 
mit is a narrow ridge, nearly circular in form. 




Copernicus, from a drawing by Sir John Herschel. 

Q. How does it appear in light of the Full 
Moon? 

A. It is exceedingly brilliant, and sometimes 
resembles a string of pearls. 

Q. What other of the Ring mountains is visible 
to the naked eye ? 

A. Tycho appears in the south-east quadrant 
of the Moon ; is fifty-four miles across, and is 
sixteen thousand feet high. 



The Eclipses. 

Q. What is an Eclipse % 

A. It is an obstruction or obscurity of the light 
of the Sun or Moon by the interposition of some 
dark body between them and our sight. 

Q. What causes an Eclipse of the Moon ? 

A. When the Moon, in its revolution around 
the Earth, passes into its shadow, she suffers an 
Eclipse ? 

Q. What is the philosophical cause of an 
Eclipse ? 

A. A body always casts its shadow in the oppo- 
site direction from which the light strikes it ; the 
Sun is the great source of light and is nearly one 



48 



ELECTRO-ASTRONOMICAL ATLAS. 



million four hundred thousand times as large as 
the Earth, hence, owing to its immense size, the 
rays of light from the Sun would pass beyond the 
Earth, and at a distance of eight hundred and 
forty thousand miles would come together; and 
the diameter of the Earth being about eight hun- 
dred thousand miles, the shadow near its surface 
would also be about the same ; but the Moon is 
only two hundred and forty thousand miles from 
the Earth ; at that distance from the Earth, the 
shadow is only about six thousand miles broad, 



and as it assumes the form of a cone, it would ter- 
minate at a point where the rays of the Sun come 
together beyond the Earth — at a distance of eight 
hundred and forty thousand miles from it. The 
diameter of the Earth being eight thousand miles, 
hence, the Moon in passing around the Earth, 
when she comes into its shadow would become 
completely immerged in it and will have to move 
two or three times her whole diameter before she 
will emerge from the shadow into the light. 



LESSON XXXII. 

Analysis. — Eclipse — When occur — Explained — When they cannot occur — Result, if the Orbits of the Earth and Moon were on 
the same Plane — Cause of an Eclipse of Sun — When only occur — Tides — How produced — Time of Spring Tides — Why ? — 
Effect of Sun — That of Sun less than Moon — Why ? 



Eclipses. 

Q. At what times only do we have an Eclipse 
of the Moon \ 

A. It can occur only at the time of a Full Moon. 

Q. Why is this so ? 

A. Because the Moon can "never get into the 
shadow of the Earth at any other time. 

Q. Why do we not always have an Eclipse of 
the Moon at Full Moon ? 



Above the Earth'- ; li;vl..w. 







Shadow below the Earth. 

Fig. 29. 
NEW AND PULL MOONS WITHOUT ECLIPSES. 



Below the Earth'.- ■■tirirl-uv. 



A. The orbits of the Earth and the Moon do 
not lie on the same plane, hence the Moon may 
sometimes pass above or below the shadow of the 
Earth, then she will not suffer an Eclipse. 

Q. What would be the result if the orbits of 
the Earth and the Moon lay on the same plane ? 



A. We should have an Eclipse of the Moon at 
every Full Moon, and an Eclipse of the Sun at 
every New Moon. 

Q. What causes an Eclipse of the Sun % 
A. The Moon, in passing around the Earth, 
when she gets between the Earth and Sun, her 
shadow being in the opposite direction from the 
Sun at that time, it can fall upon the Earth. 




PLATE XII 



li^JL 1, .... .. I 



WW W 



■'•■■■ -.:'''■■/ " V;' :; >': iy."-- 






ijiiiii 



WEED; PARSONS & CO.ALBANY, N. Y, 



Bill 



. ■ ■ ■■ 




A.TOLLE, PHOTO-LITH 



GENERAL THEORY OF ECLIPSES 



ELECTRO-ASTRONOMICAL ATLAS. 



49 



Q. Why do we have an Eclipse of the Sun only 
at New Moon ? 

A. At any other point in the orbit the shadow 
of the Moon would fall away from the Earth, 
hence, it would be impossible at any other time 
to have an Eclipse of the Sun. 



Some are 




TOTAL ECLIPSE OF THE SUN 



Eclipses of the Sun. 

Solar Eclipses are of three kinds 
total ; the dark disc 
of the Moon then 
entirely covers the 
Sun. Others are 
partial ; t h a t is, a 
portion only, large or 
small, of the Solar 
disc is eclipsed. Last- 
ly, there are annular, 
which take place 

when the disc of the Moon is not large enough to 
entirely cover that of the Sun, and leaves a lumi- 
nous ring visible 
round its own body. 

As the Moon is 
much smaller than 
the Sun, it will be 
understood that it is 
its small relative 
distance which causes 
its disc to appear of 
equal and even great- annular eclipse of the sun; theory. 

er dimensions than that of the Sun. This distance I Q. How many solar eclipses do we generally 
varies by reason of the elliptical form of its orbit, | have each year ? 
and hence the dimensions 




a total Eclipse of the Sun. Here the dark shadow 
of the Moon falls on the Earth and obscures the 
entire body of the Earth. 

Again, if the Cone of the Moon' s shadow does 
not reach the earth, there will be annular eclipses 
visible in those parts comprised in the prolonga- 
tion of the Cone ; a partial eclipse to those which 
are only found in the penumbra. This case is 
represented by the next figure. (Fig. 32.) 

It will be seen, 
therefore, that the 
conditions of the pos- 
sibility of a total 
eclipse of the Sun 
are the following : 

The Moon must be 

in conjunction, that 

is, she must be new ; 

She must at the 

same time be near a node ; 

Lastly, her distance from the Earth must be 

less than the length 

of the cone of shadow 

projected by her into 

space. 

The same condi- 
tions, except the last, 
are necessary for an 
annular eclipse. 



of the lunar disc are some- 
times larger, sometimes 
smaller than, and some- 
times equal to those of the 
Sun. If yon turn to 
Fig. 31, you will witness 




A. Two. 
Q. What is the greatest 
number possible ? 
A. It is seven. 



Fig. 33. 
PROGRESS of a central eclipse. 



50 



ELECTRO-ASTRONOMICAL ATLAS. 




The Tides. 
It is well known 
that twice a day at 
an interval of 12 
hours and 25 min- 
utes the shores of 
the ocean present us 
with the spectacle of 
the flow of the tide. 
The tide by degrees 
rises, gaining on the 
beach, which it 
covers to a greater 



Q. What phenomenon results mainly from the 
the influence of the Moon 1 

A. The Tides. 

Q. What causes the Tides ? 

A. The Earth attracts the Moon, and the Moon 
in turn attracts the Earth. The solid particles of 
matter composing the surface of the Earth not 
being free to move, the attraction of those parti- 
cles is not perceptible by us, but the particles of 
matter composing the surface of the ocean being 
free to move, the attraction is perceivable, which 
causes the water to rise and form a wave. (See 
fig. 34.) 

Q. At what time do we have spring tides 1 

A. At New Moon. 

Q. Why? 

A. The Moon is then between the Earth and 
Sun, and in range with them. 

Q. How does that effect the Tides to make 
them higher % 

A. The Sun and Moon, being on the same side 
of the Earth, and in range with it, the attraction 
of both acts together on the Earth. (See fig. 35.) 

Q. What proportion do they attract ? 

A. The Moon causes the water to rise five feet, 



and still greater 
height, and after six 
hours gains its maxi- 
mum. 

Scarcely is the in- 
stant of high water 
or flood tide attained 
then the flow or rise 
of the water ceases ; 
the descent com- 
mences, and the ebb 
succeeds to the 
flow. 



and. the Sun causes 
it to rise another 
foot, making it six 
feet. It is then high 
tide on the side of 
the Earth toward 
the Moon and on 
the exact opposite 
of the Earth, while 
at the two sides of 
the Earth it is low 
tide. 

Q. Why does not 
the Sun exert a 
more powerful at- 
traction upon the 
Earth, it being so 
much larger than 
the Moon? 

A. The Moon is 
about 91,260,000 
miles nearer the 
Earth than the Sun 
is at New Moon. 



PLATE XIII. 




WEED. PARSONS & C'.ALBANY. 



.TOLLCPMOTO-IITH. 



MARS AND THE EARTH. 

COMPARATIVE DIMENSIONS 



ELECTRO-ASTRONOMICAL ATLAS. 



51 



LESSON XXXIII. 

Analysis. — Planet Mars — Location — Appearance ; To the Naked Eye — Distance from Sun — Time around it — Indication — Time 
of Revolution on Axis — Indication ? — Diameter — Inclination — Exterior — Why ? — Resemblance to Earth — Changes of Climate 
— Divisions of Land and Water — Geography Similar — Mars Probably Uninhabited — Circumference of Orbit — Distance from 
Earth — Opposition — Where looked for — Position of the Earth — Appearance of Mars. 



The Planet Mars. 

Q. Where is Mars located in the order of the 
Planets ? 

A. He is the fourth planet in the order of dis- 
tance from the Sun, between the Earth and the 
Asteroids. 

Q. What is its appearance 1 

A. To the naked eye it is distinguished for its 
brilliant red light. 

Q. How far is this planet from the Sun ? 

A. The average distance is 145,205,000 miles 
from the Sun. 

Q. How long does it take Mars to revolve 
around the Sun ? 

A. It takes 687 days. 

Q. What does this indicate ? 

A. The length of his year. 

Q. How long does it take to turn on its axis ? 

A. Twenty-four hours and forty minutes. 

Q. What does this show? 

A. The length of his day. 

Q. What is his diameter % 

A. It is 4,200 miles. 

Q. What is the inclination of the plane of 
his orbit to that of the Ecliptic ? 

A. One degree and fifty-three minutes. 

Q. Is Mars an interior or exterior planet ? 

A. He is an exterior planet. 

Q. Why? 

A. Because he lies wholly beyond the 
orbit of the Earth. 

Q. To what globe has Mars a near resem- 
blance ? 



Q. Are there similar changes of cold and heat 
in Mars as in the Earth \ 

A. At certain seasons Winter scenes are pre- 
sented, and at others, rain is apparent and the 
snow-caps disappear. 

Q. Are there other analogies \ 

A. In divisions of seas and land. 

Q. Any thing known of its geography 1 

A. It is nearly as well known and as well de- 
fined as that of the Earth. See Fig. 36. 

Q. Is there evidence that Mars is inhabited ? 

A. The conditions of life on these planets are 
so unequal, it seems hardly possible or even pro-' 
bable, for Mars to be inhabited. 

Q. What seems to confirm this position 1 

A. Mars receives but one half the amount of 
heat or light enjoyed on the Earth, hence, the 
apparent impossibility of human existence. 



A. The Earth. 

Q. In what respects 

A. In climates. 




this manifest ? 



CHART OF MARS, FROM DRAWINGS BY MR. DAWES 



Q. What is the circumference of its orbit ? 
A. It is 901,064,000 miles. 



52 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. What is the mean distance of Mars from the 
Earth ? 
A. He is 50,000,000 miles. 
Q. Is he then in conjunction or opposition ? 
A. In opposition = 

Q. Which way do we look to see him ? 
A. In the direction opposite to the Sun % 



Q. Then where would be the position of the 
Earth % 

A. Between the Sun and Mars. 

Q. At this time what is the appearance of Mars % 

A. It appears with a surface twenty-five times 
larger than when in his conjunction % 




LESSON XXXIV. 

Analysis. — When take place — Cause of brilliancy — Distance one side of Orbit — Inclination — Rate of Motion — Light, compared 
with that of Earth — Difference of Diameters — Density, compared with the Earth — Difference of Weight — Ratio from Sun of 
the Orbits of Planets described — -Rapid Changes — White Spots — Snow Zones. 

Q. When does this take place % 

A. When he is in that part of his orbit 
beyond the Sun from the Earth and in range 
with them. 

Q. When he is in his superior conjunction 
how far is he from the Earth ? 

A. He is 240,000,000 miles. 

Q. Does this account for the changes in 
the size and brilliancy of the planet ? 

A. It does. 

Q. How far is the Sun one side of the orbit 
of Mars ? 

A. He is 13,463,000 miles. 

Q. What is the inclination of his axis to the 
plane of his orbit ? 

A. It is thirty degrees and eighteen minutes. 

Q. What is Mars' rate of motion in his revolu- 
tion around the Sun ? 

A. It is 54,640 miles an hour. 

Q. What proportion of light falls upon Mars 
compared to that on the Earth ? 

A. About one-half as much. 

Q. What is the difference between the polar 
and the equatorial diameter of Mars ? 

A. It is two hundred and sixty -three miles. 



BIAlIKTir. OF MAKS AT EXTREME LEAST AND MEAN DISTANCES. 

Q. What is the density of Mars compared with 
the Earth I 

A. It is much less. 

Q. How much would a body weigh on the 
planet Mars that weighs one pound on the Earth? 

A. It would weigh 5 ounces and 6 drachms. 

Q. What is the ratio of the distance from the 
Sun, of the orbits in which the planets already 
described move % 

A. Venus' mean distance is about twice as far 
as Mercury ; that of the Earth twice as far as 
Venus, and the mean distance of Mars twice as 
far as the Earth. . 



PLATE 



_§SL 



4,0 



»o\0 



_ ^ ~l\0 &\o ■ 



"£??*. 



Exhibiting the re lativ e ^Position of the 
an3 their Inclination to the -Plane I 



:« 




/%z£ ofMm-s Inclination 'l °5/~ 

VUme ^pf Tr arms' JheWwK on 

EQJffTIC orOrbi%oftheEartk 






^~: 



J^Jhernluml of the Zodi, 



J 




> IncknMt&qf Jtg>iter I 18 ^ 
\lhcYination tf'Satont. ?_*>*?.. 




W. 



COMEdJRATIVE DISTANCES of at 



tttl 









1 



(1- 



DISTANCES of the SATELLITES from their sever 



Scale of Senxidiameters of W • 



30 SATURN 



Scale of ' SemidJameters of % 



70 



20 



JUPITER and Fonr Satellites 

-o « »- 

JVrnrfr of Semi diameters of 3 ■ 

70 




JPLAJXETS jfrojm: tse SUJST. 



no no 



140 ISO 



170 180 



PRIMARIES iix Semi diameters of the latter 
l-Fii/Tit Satellites 



— ; ® a 




<J# 


I £tg7vt Satellites. 






7* 


& 


30 






^ EARTH and One Satellite. 






Scale of Senridiameiers of s 







ELECTRO-ASTRONOMICAL ATLAS. 



53 



There are constant and rapid 
changes going on, as in Fig. 38. Yon 
perceive the change manifest in an 
interval of two honrs. These changes 
in the brightness of the disc are 
owing, it is supposed, to the varia- 
tions of the clouds of vapor in its 
atmosphere. 

No mountains have yet been dis- 
covered. In the region of the poles 
are brilliant white spots, which are 
supposed, by some, to be masses of 
Snow. These Snow Zones recede in 
summer and increase on the approach of winter. 

Hence, we can observe in fact most, if not all, 
the changes of the seasons which take place on 
the surface of our neighboring planet. 




HOURS' INTERYAL. (WARREST DE LA RUE.) 



Q. What small planets lie between Mars and 
Jupiter % 
A. They are the Minor Planets. 



LESSON XXXV. 

Analysis.— The Minor Planets — What are they ? — Number — Space occupied — Kepler's impression — Not witnessed in his Day — 
Two Hundred Years after — Discovery Made — Four Found — Ceres, Pallas, Juno and Vesta. 



The Minor Planets. 

Q. Where are the Minor Planets 1 

A. There are a large number of Minor Planets 
lying between Mars and Jupiter. 

Q. How many do they number 1 

A. There are now known to be one hundred 
and thirty-four Minor Planets. 

Q. How large a space do they occupy 1 

A. Not less than 35,000,000 miles. 

Q. What impression was made on the mind of 
Kepler in view of this unoccupied space ? 

A. He was of opinion that within that space 
there must lie an undiscovered planet. 

Q. How long after his day before a thorough 
research was made ? 

A. Some two hundred years. 



Q. Who commenced it ? 

A. Twenty-four Scientific Explorers, in 1800, 
commenced a search for the hidden planet. 

Q. Who was the first to detect the new planet % 

A. It was an Italian astronomer by the name 
of Piazzi, in 1801, and called it Ceres. 

Q. What effect did this discovery produce on 
the Scientists of that day \ 

A. It gave a new impulse to astronomical 
investigations. 

Q. What was the result ? 

A. Not simply one but four were discovered. 

Q. What were they named % 

A. They were called Ceres, Pallas, Juno and 
Vesta. 



54 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSONXXXVI. 

Analysis. — Ceres — Time and by whom discovered — Estimate by Sir W. Herscbell — Diameter — Distance from Sun — Time 
around it — Inclination — Appearance in Size and Color — Pallas — Time and by whom Discovered — By whom Measured — Dis- 
tance from Sun — Time around it — Inclination — Appearance as to Size and Color — Juno — Time and by whom Discovered — 
By whom Estimated — Appearance as to Size and Color — Distance from Sun — Time around it — Inclination of Orbit — Vesta — 
Time when and by whom discovered — Comparison with the other Minor Planets — Diameter — Distance from Sun — Time of 
Revolution — Inclination of Orbit — Description of all nearly the same. 



Ceres. 

Q. In what year and by whom was Ceres dis- 
covered ? 

A. In the year 1801, by Professor Piazzi, an 
Italian astronomer of Palermo. 

Q. Who has given the most accurate estimate 
of this planet ? 

A. Sir Wm. Herschell. 
What is its diameter ? 
It is 163, miles. 

What is her mean distance from the Sun 1 
It is 262,764,110 miles. 

Q. How long does it take to revolve around the 
Sun? 

A. It takes about 1680 days. 

Q. What is the inclination of her orbit to the 
plane of the Ecliptic ? 

A. It is ten degrees and thirty-seven minutes. 

Q. What is its general appearance as to color 
and size ? 

A. This planet shines with a pale, reddish 
lustre, and like a star of the eighth magnitude. 



Pallas. 



Q. At what time and by whom was this dis- 
covered ? 

A. On the 28th of March, 1802, by Dr. Olbris. 

Q. Of whom has been received the most reli- 
able measurement of this planet ? 

A. It has been given by Dr. Lamont of Munich. 

Q. What is its mean distance from the Sun ? 

A. It is 263,186,670 miles. 



Q. What is the time of its revolution ? 

A. It is one thousand six hundred and eighty- 
four days. 

Q. What is the inclination of the plane of its 
orbit with the plane of the Ecliptic ? 

A. It is thirty-four degrees thirty-seven min- 
utes and twenty seconds. 

Q. What is its appearance as to size and 
color ? 

A. It shines like a star of the seventh magni- 
tude and is of a yellowish light. 



Juko. 



Q. Who discovered Juno, and in what year ? 

A. It was discovered by Professor Harding, of 
Lilienthal, on the 1st of September, 1804. 

Q. What is its appearance as to size and color? 

A. This planet shines as a star of the eighth 
magnitude and is of a reddish color. 

Q. What is its mean distance from the Sun ? 

A. It is 253,524,410 miles. 

Q. What is the time of its revolution around 
the Sun ? 

A. It is one thousand five hundred and thirty- 
two days. 

Q. What is the inclination of the plane of its 
orbit to the plane of the Ecliptic ? 

A. Thirteen degrees three minutes and seven- 
teen seconds. 



Vesta. 
Q. At what time and by whom was Vesta dis- 
covered ? 



ELECTRO-ASTRONOMICAL ATLAS. 



55 



A. She was discovered by Dr. Olbris, on the 
29th of March, 1807. 

A. How does she compare with the minor 
planets ? 

A. She is a small planet of the sixth or seventh 
magnitude, yet, when she appears in opposition 
to the Sun, she appears the brightest of all the 
Minor Planets. 

Q. What is her diameter ? 

A. She is only 295 miles in diameter. 

Q. How far is she from the Sun 1 

A. She is 224,327,205 miles. 

Q. What is the period of her revolution % 

A. It is one thousand three hundred and 
twenty-five days. 

Q. What is the inclination of the plane of her 
orbit to that of the Ecliptic ? 

A. It is seven degrees eight minutes and 
twenty-five seconds. 

Note. — The Minor Planets are so nearly similar, that it is 
speak further of them separately. 




Fig. 39. 

< .'. [PAKAT1YE DIMENSIONS OP THE EARTH AND JUNO, 
CEKES PALLAS AND VESTA. 



The foul- 
planets of 
which we have 
just given some 
details, are 
among the 
most important 
of the group. 
The smallness 
of nearly all the others is such that it is not possi- 
ble to measure their diameters, as they appear 
in a telescope merely as luminous points. It is 
probable that the least of these microscopic bodies 
have diameters which do not reach many score 
miles, and that a good walker could easily in a 
day make a tour of many of these miniature 
worlds. 

Q. How long shall we go on making discoveries 



of fresh bodies in this zone between Mars and 
Jupiter % 

A. This is a difficult question to solve, but 
it is probable that we are now acquainted, if not 
with the largest of the Minor Planets, at all events 
with all those most easily visible from the Earth. 
The discovery of others will, therefore, become 
more and more difficult, and the extension of 
their number is partly subordinate to the use of 
larger instruments in the research, and more 
detailed celestial maps. At all events, M. Lever- 
rier, from mathematical considerations, has as- 
signed to the total mass of the bodies which com- 
pose the ring, such a limit, that if we suppose 
them to possess a density equal to that of our 
own globe, those already discovered form only 
the T^nrth P ar t 0I> it- This would make the num- 
ber of the Minor Planets about 150,000. But, 
admitting that this number may be excessive, and 
in reducing it to the tenth of its value, this swarm 
of celestial bodies will still be counted by 
thousands. 



JUPITER. 

From that region of space where we have just 
seen the smallest members of our system circula- 
ting in their orbits, we pass without transition to 
the largest planet — the colossal Jupiter. 

To the naked eye, Jupiter appears as a star of 
the first magnitude, the brightness of which, vari- 
able with its distance from the Earth, is some- 
times, when the Moon is absent, sufficient to throw 
a shadow. Its light is constant, and scintillates 
but rarely. But if, to examine it, a rather power- 
ful telescope is used, the point expands into a 
well-defined disc, and is generally seen to be 
accompanied by three or four little points of light 
which oscillate in short periods of time round the 
central planet : These are the Satellites of Jupiter. 

Yenus, Mercury and Mars, as we have seen, 



56 



ELECTRO-ASTRONOMICAL ATLAS. 



are without satellites ; the Earth has only one. 
Jupiter with its four moons, which the powerful 
attraction of its bulk compels to revolve round 
him, exhibits to us, therefore, a' small system 
analogous to the solar one of which it forms part 
and which it reproduces on a smaller scale. 

To arrive in our journey from the Sun as far as 
the Jovian system, we must pass over a distance 
which exceeds five times the mean distance of the 
Sun from the Earth, or, in the mean, 500,000,000 
miles. But the orbit described by Jupiter round 
the Sun differs from the circular form more than 
does the Earth's. Its distance, therefore, is more 
variable, and while at Perihelion it reaches 472,- 
000,000 miles, at its greatest distance it is not less 
than 520,000,000 miles from the Sun, hence the 
difference being 48,000,000 miles. 

Jupiter, therefore, as seen from the Sun, pre- 
sents an apparent diameter sometimes greater, 
sometimes less than its mean one ; and, of course, 
the same phenomenon is seen by observers situa- 
ted on the Earth, but in a much greater propor- 
tion. Fig. 40 will give an idea of the variations 




JTTPITKK'S MEAN AND EXTREME DISTANCES FROM THE EARTH. 

of size which the disc of Jupiter, at the time of 
its mean and extreme distances from the Earth, 
presents to us. 



The reason of this difference between the appa- 
rent diameters of the disc is easily explained. 
The orbit of Jupiter, like that of Mars, encircles 
the terrestrial one, and the motions of the two 
bodies in their respective orbits bring them, once 
in every thirteen months, in the same straight 
line with the Sun, and on the same side of it ; 
Jupiter is then in opposition, and its distance 
from the Earth is measured by the difference of 
the distances of the two bodies from the Sun. 
In a similar period the two planets are still in a 
straight line with regard to the Sun, but on oppo- 
site sides of it. This is the conjunction of Jupi- 
ter, and the distance of the two planets is found 
by adding their respective distances from the Sun. 
These distances themselves are sometimes smaller 
and sometimes greater than at others, and there- 
fore the same thing happens with regard to those 
which separate the Earth from Jupiter at the 
time of opposition and conjunction. 

At its greatest distance from the Earth, Jupiter 
is 617,000,000 miles from us ; at opposition it 
may be within 375,000,000 miles ; but in the mean, 
the distance of Jupiter at conjunction with the 
Sun is 591,000,000 miles, and at opposition 400,- 
000,000 miles, the difference being the diameter of 
the Earth's orbit. 

From the preceding numbers we may perceive 
the immense development of the orbit described 
by this member of our planetary system. Thus, 
to traverse this path, it requires twelve years. 
This gives a mean rate of upwards of 700,000 
miles a day, or nearly 30,000 miles an hour. 

The movements with which we are acquainted 
on the Earth can give us no idea of such a mass 
traveling eternally through the depths of space 
with a velocity eighty times greater than that of a 
cannon ball. 



PLATE XV. 









■ ■■ ^ B| 
H 

v , . ■ ■ •: 

# - 

..." 


Mr? *■ 


Mr 

wum 

■■"':' ■ ' ■.. ' ' ■■ ' " -■■■ 






im ■■' ■■■■■-■■■ > 
* - 

: -■'"•■ £'.-,:. ' k ■"■■ -'-■ ' . ■- ' 






.:■ ■ ■ • 


■ ■■ ' '"--■' -.' "' '-'• 






'^Ute 


- 






" 



WEED, PARSONS* C?.ALBANY. 



A.TOLIE, PHOTO. LITH. 



JUPITER. 



J7rt<?/it and dark belts, transit ofa Satellite and its shadow across thedisk 



ELECTRO-ASTRONOMICAL ATLAS. 



57 



LESSON XXXVII. 

Analysis. — Planet Jupiter — Situation — "Why Distinguished — Distance from the Sun — Time around it — Indication — Diam- 
meter — Time of Revolution on its Axis — Indication — Circumference of Orbit — Rate of Motion — Effect of Motion on the 
Weight of Bodies on his Surface — Weight of Bodies on his Surface compared with their Weight on the Earth — Cause of 
Difference — Satellites — Variable Appearance — Observations of Mr. 



JUPITER. 

Q. What planet lies next to the Minor Planets 
in the regular order from the Sun % 

A. It is Jupiter. 

Q. For what is Jupiter distinguished ? 

A. He is regarded the largest and most magnifi- 
cent planet of the Solar System. 

Q. How far is Jupiter from the Sun ? 

A. He is 495,817,000 miles. 

Q. How long does it take this planet to make a 
revolution around the Sun ? 

A. It takes him 4,332 days 14 hours and 2 
minutes, or nearly 12 years. 

Q. What does this indicate % 

A. The length of his year. 

Q. What is the mean diameter ? 

A. It is eighty-nine thousand miles. 

Q. How long does it take Jupiter to turn on 
his axis ? 

A. It takes 9 hours and 56 minutes. 

Q. What does this show % 

Q. The length of his day. 

Q. What is the circumference of this orbit ? 

A. It is 3,110,000,000 miles. 

Q. What is his rate of motion % 

A. It is estimated at 30,000 miles an hour. 

Q. What is said of his motion on his axis ? 

A. It is said to be greater than that of any 
other planet in the Solar System. 



Q. What effect does this rapid motion on his 
axis have upon the weight of bodies on his surface ? 

A. It makes them lighter than they would be 
were its motion no greater than that of the Earth. 

Q. What is the weight of bodies on the surface of 
Jupiter compared with their weight upon our 
Earth? 

A. A body that weighs one pound upon the 
Earth at the Equator, would weigh two pounds 
four ounces and a half on the Equator of Jupiter. 

Q. What causes the difference ? 

A. The immense size of Jupiter. 

Satellites. 

Four luminous points — four small stars — un- 
ceasingly accompany Jupiter in its twelve-yearly 
revolution. They are easily observed with small 
telescopes. 

From hour to hour their positions vary, and 
they seem to oscillate from one side to the other of 
the disc, in paths nearly parallel to the direction of 
the belts, that is to say, to the equator of Jupiter. 
These are its moons or satellites. They are be- 
sides frequently seen to disappear, one, two, and 
even three at a time. It sometimes, indeed, even 
happens that not one of the four is visible. Jupi- 
ter then appears alone, deprived of its companions. 
This state of things was observed by Mr. Dawes, 
on the 27th of September, 1843. But it only hap- 
pens very rarely. 



58 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON XXXVIII. 

Analysis.— Satellites of Jupiter — Number — Names — Diameters — Distances — and Revolutions — Eclipses — Number per Month - 
Eclipse of Sun effected by them — Inclination of the Axis of Jupiter to Plane of his Orbit — Plane of Orbit to Plane of Ecliptic - 
Eccentricity of Orbit — Solar heat compared with Earth. 



Lastly, as mentioned, above, it may happen 
that during the disappearance of the three 
satellites, the fourth is between the Earth 
and the planet. Then the planet equally 
appears solitary and deprived of its com- 
panions. 

Fig. 42 will render clear the various posi- 
tions which the satellite may occupy with refer- 
ence to the Earth. One of them in this figure is 
represented Eclipsed, the other is seen projected 
on the disc, on which also its shadow is thrown ; 
a third is hidden by the planet, and the fourth is 
entirely visible. 




Fig. 41. 

JUPITER AND ITS FOUR SATELLITES. 

Q. How many satellites has Jupiter ? 

A. Four. 

Q. What are they called % 

A. Io, Europa, Ganymede and Callisto. 

Taking these satellites in the order of their 
distances, the times of their revolutions are as 
follows : 

First satellite ( Io ) . . . 1 day, 18 hours, 28 minutes. 
Second " (Europa) . 3 " 13 " 43 " 
Third " (Ganymede) 7 " 3 " 43 " 
Fourth " (Callisto) . 16 " 16 " 32 " 

In comparing these times with that of the 
revolution of the Moon, it is seen that the 
movements of the satellites of Jupiter are 
much more rapid than that of our Moon. This 
rapidity is the more marked, as their distances 
from the planet, and, therefore, the lengths of 
their orbits are more considerable than in the case 
of our satellite. Measured from the center of the 
planet, the mean distances of these satellites are as 
follows : 

Q. What are their respective diameters, distan- 
ces and periods of revolution around their 




primary % 












A. 


Diameter. 

Miles. 


Distance. 
Miles. 


Days. 


Revolution. 
H'rs. Mill. 


Sec. 


Io . . . 


2,440 


278,500 


1 


18 27 


34 


Europa . 


2,190 


443,000 


3 


13 14 


36 


Ganymede 


3,580 


707,000 


7 


3 42 


33 


Callisto . 


3,060 


1,243,500 


16 


16 31 


50 



DIMENSIONS OF THE SATELLITES OF JUPITER COMPARED WITH THOSE OF 
THE EARTH AND MOON. 

We have seen what are the apparent dimen- 
sions of the four satellites as seen from Jupiter, 
compared to the apparent size of our Moon. But 
we must not confound the apparent with the real 
diameters. ( See the above table of diameters.) 
So, the third and fourth in the order of distance 
are the first and second in order of magnitude ; 
one only is less than our Moon ; taken together, 
they would form a body 9£ times larger than it, 
or about one-fifth of the volume of the Earth. 

Lastly, the volume of the largest exceeds by 



ELECTRO-ASTRONOMICAL ATLAS. 



59' 



two-thirds the volume of the planet Mercury. 
Here, then, we have a secondary body larger than 
a primary one of the first order, and far surpass- 
ing in size those which circulate between Mars 
and Jupiter. 



Eclipses of these Satellites. 

Q. How many Eclipses do they suffer every 
month ? 

A. The first suffers eighteen ; the second, eight 
or nine ; the third, about four. The fourth does 
not suffer as much as either of the other three, as 
it frequently passes its opposition without being 
involved in the shadow of Jupiter. 

Q. When either or all of them are between 
Jupiter and the Sun, what takes place ? 

A. Their shadows fall upon the planet as they 
come between it and the Sun, causing an eclipse 
of the Sun. 



Q. How many can cause an eclipse at a time ? 

A. All of them can never be eclipsed or cause 
an eclipse at the same time ; seldom ever but two 
of them. 

Q. What is the inclination of Jupiter' s axis to 
the plane of his orbit \ 

A. Eighty-six degrees and fifty-four and a half 
minutes, or three degrees and five and a half 
minutes from the perpendicular. 

Q. What is the inclination of the plane of his 
orbit to the plane of the ecliptic ? 

A. One degree and nineteen minutes. 

Q. What is the eccentricity of the orbit of 
Jupiter ? 

A. It is 23,810,000 miles. 

Q. What is the intensity of its solar heat when 
compared with the heat of the Earth \ 

A. It is twenty-seven times less. 



LESSON XXXIX. 

Analysis.— Observations of Astronomers — Appearance of Belts — What known — Situation — How esteemed by Astronomers — Uni- 
formity considered — Other peculiarity of appearance — Accounted for — Difference of Jupiter's Diameters. 

Q. What is the appearance of these belts ? 

A. They appear like dark stripes across the 
disc of this planet. 

Q. What is known of these belts % 

A. They are known to vary as to their number, 
distance from each other and their positions. 

Q. How do they appear to be situated % 

A. Parallel to one another and to the equator 
of Jupiter. 

Q. How are these regarded by astronomers ? 

A. They are esteemed by some to be openings 
in the luminous atmospheric envelope of Jupiter, 
by others that openings betray the dark surface 
of the planet, and that glimpses thus caught of 
the solid body constitute the narrow, dusky belts 
or bands. 




TELESCOPIC TIE1V OF JTJPITEK. 



Q. What has been particularly observed by 
astronomers relative to the planet Jupiter ? 

A. On certain occasions as many as eight belts 
have been seen, at others only one. 



60 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. Are they at all times the same in length and 
width ? 

A. They continue for months without variation, 
and a new belt is seen to form in a few hours ; 
sometimes they decrease in length and then in- 
crease in width until they run into each other to 
the extent of five thousand miles in breadth. 

Q. What other peculiarity is manifest in their 
appearance ? 

A. There are at times seen bright and dark 
spots in these belts, which usually disappear with 



the belts, sometimes they continue. Cassini ob- 
served one in the same position for forty years. 

Q. How are these belts and spots accounted 
for? 

A. They are regarded as nothing more than 
atmospheric phenomena resulting from the rapid 
motion of the planet on its axis. 

Q. What is the difference between the Equato- 
rial and the Polar diameters of Jupiter ? 

A. The Equatorial is sixty -three hundred miles 
the longer. 



LESSON XL. 

Analysis. — Saturn — Situation — Distance from Sun — Time round it — Indication — Diameter — Revolution on Axis — Indication — 
Inclination of Axis to its Orbit — Inclination of Orbit to the Ecliptic — Eccentricity of its Orbit — Difference of Diameters — Solar 
Light compared with that of Earth — Rate of Motion — Density — Difference of Weight — Why one of the most magnificent 
Planets — Rings and Moons. 



Saturn. 

Q. Where is the planet Saturn situated ? 

A. Next to Jupiter, in the order of distance 
from the Sun, and between the orbits of Jupiter 
and Uranus. 

Q. What is the distance of Saturn from the 



Sun 
A. 

Q, 



It is nine hundred and seven million miles. 
What is the diameter of this planet? 

A. It is seventy-nine thousand miles. 

Q. How long does it take to make a revolution 
around the Sun ? 

A. It takes twenty-nine and a half years. 

Q. What does this show ? 

A. It indicates the length of its year. 

Q. How long does it take Saturn to turn on its 
axis ? 

A. Ten hours and sixteen minutes. 

Q. What does this indicate ? 

A. The length of her day. 



Q. What is the inclination of its axis to the 
plane of its orbit ? 

A. It is perpendicular. 

Q. What is the inclination of its orbit to the 
plane of the Ecliptic ? 

A. Two degrees and twenty-nine and a half 
seconds. 

Q. What is the eccentricity of its orbit ? 

A. It is forty-nine million miles. 

Q. What is the difference between its Equato- 
rial and Polar diameters ? 

A. The Equatorial is six thousand and seven 
hundred miles longer than its Polar. 

Q. What proportion of solar light does this 
planet receive compared with that of the Earth ? 

A. It is about one-nineteenth part of the 
amount of light. 

Q. What is its rate of motion ? 

A. It is twenty-two thousand miles an hour. 

Q. What is the density of this planet ? 

A . It is about as great as cork. 



PLATE XVI 




WEED. PARSONS ft C0.,AIBANY,N.Y. A.TOUE, PHOTO-LITH. 

SATU RIM. 

Front fffrservations ofHond, Striwe and Warren JPeZaMwM&./8J2,andMar./8$6. 



ELECTRO-ASTRONOMICAL ATLAS. 


61 


LESSON XLI. 




Analysis. — Rings of Saturn — Situation of them — Revolution — 


Detached — How known to he Separate — Distance from Planet to 


Interior Ring — Breadth of it — Width between Rings — Thickness of Rings — Consists of what — 


How determined — Importance 


of them to the planet. 






Q. A body that weighs one pound on the sur- 


A. It would weigh about twenty-seven and a 


face of the Earth would weigh how much on the 


half pounds. 




surface of Saturn % 


Q. Why is the planet 


Saturn considered one 


A. One pound and four drachms. 


of the most magnificent and interesting objects in 


Q. How much would a body that weighs one 


the planetary system % 




pound on the surface of the Earth, at the equator, 


A. It is attended with eight moons and a suite 


weigh if transported to the Sun ? 


of gorgeous rings. 




Rings of 


Saturn. 


Q. What is the 


Q. How are the 






rings of Saturn situ- 






breadth of the interior 


ated in regard to each 






ring % 


other and to the 






A. It is nineteen 


planet ? 




"■ ^^jjT: /^ffl 


thousand and fifty 


A. They are con- 


^^r 


^/y^ 


miles. 


centric, or one lies 




, wnMm 


Q. What is the 


between the other and 




syyyWffi;i 


width of the opening 


the planet, and they 


L| 1 


' J^J&w jfifcfifo- 


between the two 


are over the equator 


^ i ,/s 




rings \ 


of the planet. 


WrsJwRk. ly\*-jS 


jr JEk£?L>^' 


A. It is two thou- 


Q. How do they 




.^Khw^' ,v hH 


sand and nine hun- 


revolve % 


Vf '■■■■■■^\^mmtk 




dred miles. 


A. On their axis and 






Q. What is the 


in the same time. 






breadth of the ex- 
terior ring % 


Q. How do we 


Pig 


44. 


- , -, SATUBN AND THE EABTH : 

know they are sepa- 


30MPARATIVE DIMENSIONS. 


A. It is seven 


rate or wholly detached from each other \ 


thousand and three hundred miles. 


A. The fixed stars have been seen in the dis- 


Q. What is the thickne 


ss of the rings. 


tant heavens through the openings between them 


A. They are not more 


than one hundred miles 


and between the planet and the first ring. 


in thickness. 




Q. What is the distance from the planet to the 


Q. Of what do they consist ? 


interior ring % 


A. Various opinions ai 


e entertained as to their 


A. It is thirty-three thousand and six hundred 


composition ; some that 


they are a solid com- 


and fifty miles. 


pact substance, and others that they are fluid. 


16 







62 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. What reason have they for the latter con- 
clusion ? 
A. It is the fact they are almost infinitely divided. 



Q. What importance are they to the planet ? 
A. They serve to reflect light upon its surface. 



LESSON XLII. 

Analysis. — Circles not True — Centers coincide with the Center of Planet — Gravity of These Rings — Importance to the Stability of 
the System of Rings — Moons of Saturn — Number — Seldom Seen — Revolve with the Rings — Respective Distances from 
Inclination of their respective Orbits to the Plane of Saturn — Eclipses of these satellites — Seldom Suffer Respective 



Saturn - 



Q. Are they in true circles % 

A. They are not exactly. 

Q. Does the center of their rings coincide with 
the center of the planet. 

A. It does not exactly. 

Q. What is known of their centers of gravity ? 

A. The center of gravity of these rings oscil- 
lates around that of the planet, describing a small 
orbit. 

Q. What importance is this to the stability of 
the system of rings ? 

A. It prevents the rings from being shifted from 
their equilibrium by any external force or attrac- 
tion of other heavenly bodies. 

We give below the names of the eight moons 
of Saturn, with their distances from the center of 
the planet, and the time of their revolution in 
terrestrial mean solar days : — 





Distance from Saturn's Time of Siderial Revolution. 
Center in Miles. Days H'rs. Mill. Sec. 


Mimas . . 


119,725 . . . 


22 27 23 


Bnceladus . 


153,630 . . . 


1 8 53 7 


Tethys . . 


190,225 . . . 


1 21 18 26 


Dione . . 


243,670 . . . 


2 17 41 9 


Rhea . . . 


340,320 . . . 


4 12 25 11 


Titan . . 


788,915 . . . 


15 22 41 25 


Hyperion . 


. 954,160 . . . 


21 7 7 41 


Japetus . . 


. 2,292,790 . . . 


79 7 54 40 



The first four satellites are all nearer to Saturn 
than the Moon is to the Earth. Mimas is, more- 
over, but 82,000 miles from Saturn's surface, and 
Dione about 206,000 ; Mimas' distance from the 



edge of the ring being but about 31,000 miles. 
On the other hand, Japetus is nearly ten times 
more distant from Saturn than we are from our 
satellite, so that the diameter of the Saturnian 
system measures nearly 4,500,000 miles. 




The Moons of Saturn. 

Q. How many 
moons o r satel- 
lites 'has Saturn ? 

A. Eight. 

Q. Are they 

easily discovered? 

Fig. 4 5 . A - The 7 ar e 

AND ITS SATELLITES. (SIR JOHN HEKSCHEL.) Only SCen Witll 

good instruments and under favorable circum- 
stances. 
Q. When is the best time to take a view of 

them? 
A. When the planet is at its Equinox, then the 

rings are nearly invisible. 

Q. How do these satellites revolve ? 

A. They revolve eastward with the rings of the 
planets ; in orbits nearly circular, and, with the 
exception of the eighth, in the plane of the rings. 

Q. What are their respective distances from the 
planet ? 

A. The distances and periods of the satellites 
of Saturn are as follows : 



PLATE XVII 




WEED, PARSONS 8. CO. ALBANY, N 



Time, photo- 



URANUS AND THE EARTH 

COMPARATIVE DIMENSIONS. 



ELECTRO-ASTRONOMICAL ATLAS. 





Distances la Mile 


Periodic fme 






Mimas . 


123,000 


. 00 days 


, 22 hours. 




Enceladus 


128,000 


. 1 *' 


8 


" 




Tethys . 


190,000 


. 1 " 


21 


" 




Dione 


251,000 


. 2 " 


17 


" 




Rhea 


351,000 


. 4 " 


12 


" 


55 seconds 


Titan . 


811,000 


15 " 


22 


" 


51 " 


Hyperion 


2,766,000 


79 " 


7 


" 


54 " 


Japetus . 


2,336,000 


46 " 


12 


" 


00 



Q. Wliat is the inclination of their respective 
orbits to the plane of Saturn's orbit ? 

A. The orbits of the six inner satellites are in- 
clined about thirty degrees ; the other two about 
twenty-four degrees and forty-five minutes. 



Q. What is known in regard to these satellites 
suffering eclipses ? 

A. They seldom suffer an eclipse, and they 
happen only when the rings are seen edgewise. 

Q. What is the respective sizes of these satel- 
lites? 

A. The two nearest to Saturn are the smallest, 
the third and fourth the next in size, the fifth and 
sixth are somewhat larger, the seventh and eighth 
are the largest. The eighth is about four thou- 
sand two hundred miles in diameter and turns on 
its axis, and it is probable all the others do the 
same. 



LESSON XLIII. 

Analysis. — Uranus — Situation — Distance from Sun — Time of Revolution round the Sun — Diameter — Time of Revolution on 
Axis not known — Inclination of Orbit — Rate of Motion — Light compared with that of the earth — Density — Eccentricity of 
Orbit — Difference of the Weight of Bodies on the Earth and the Surface of Uranus — Satellites of Uranus — Number - 
tive Distances and Periodic Times — Their Variation in Revolution — Size of them — Seldom suffer Eclipse. 



Uranus. 

Q. Where is the planet Uranus situated ? 

A. Uranus is the eighth planet in the order of 
distance from the Sun, its orbit lying between the 
orbits of Saturn and Neptune. 

Q. How far is Uranus from the Sun % 

A. It is 1,824,000,000 miles. 

Q. How long does it take this planet to revolve 
around the Sun ? 

A. It takes eighty-four years. 

Q. What is the diameter of Uranus ? 

A. It is thirty-five thousand miles. 

Q. How long does it take to turn on its axis % 

A. Owing to its immense distance from the Sun 
its diurnal motion has not as yet been ascertained. 

Q. What is the inclination of its orbit to the 
plane of the ecliptic ? 



A. It is but very little inclined ; forty-six min- 
utes and twenty-six seconds. 

Q. What is its rate of motion \ 

A. It is fifteen thousand miles an hour. 

Q. What is the proportion of light of this 
planet compared with that on the Earth \ 

A. It is three hundred and sixty times less. 

Q. What is the density of this planet % 

A. About that of water. 

Q. What is the eccentricity of its orbit ? 

A. It is eighty-five million miles. 

Q. What would a body weighing one pound on 
the Earth' s surface weigh if removed to the planet 
Uranus % 

A. It would weigh fourteen ounces and four- 
teen drachms. 



64 



ELECTKO-ASTRONOMICAL ATLAS. 



Satellites of Ukantts. 
Uranus, like Saturn, is the center of a little 
system, comprising, besides the principal planet, 
eight moons or satellites, revolving in planes 




nearly perpendicular to the plane of the planet' s 
orbit. These bodies, whose revolutions are accom- 
plished, the nearest in two days, and the most 
distant in about 108 days, possibly compensate, 
in some degree, by their reflected light, during 
the nights of the planet, the feeble intensity of 
the daylight. The Sun is visible at Uranus as a 
small disc, whose superficial extent is but one 
370th of the extent of the solar disc as seen from 
our globe. The heat received from it, too, is but 
one 370th of that we receive from the Sun. 

We have shown in fig. 47, the relative dimen- 
sions of the orbits of the satellites, as they would 
be seen if we could obtain a bird's-eye view of 
the plane in which they revolve. We have 
already mentioned the fact that their movements 
are performed in a direction nearly perpendicular 
to the plane in which the planet revolves around 
the Sun. Another peculiarity, and this is found 
nowhere else throughout the solar system, further 
distinguishes Uranus — the direction of these 
movements is retrograde ; that is to say, it is con- 
trary to that of all the other known movements 
of satellites and planets. But this anomaly prob- 
ably results from the very great inclination of 
their orbits, shown in fig. 47. 






/ / 6 




The first satellite is but 128,000 miles, or about 
half the distance of our Moon, from the planet. 
The most distant of the four of which we have cer- 
tain knowledge is 392, 000 miles. Of these four, the 
two nearest, Ariel and Umbriel, were discovered 
by Lassell and Otto Struve respectively ; the six 
remaining ones (two of which have received the 
names Titania and Oberon), by Sir W. Herschel. 



Q. How many satellites has Uranus % 
A. It has eight ? 

Q. What is their respective distances 
period of times % 



and 



First Satellite 224,000 

Second " 296,000 

Third " 340,000 



Fourth Satellite 390,000 11 10 56 29 
Fifth " 777,000 38 48 84 00 

Sixth " 1,556,000 107 16 39 56 



Note. — Of the remaining two but little 
but little can be said. 



known, and hence 



Q. In what respect do the satellites of Uranus 
vary from the analogy of the motion of all the 
other satellites in our planetary system ? 

A. Their motions in their orbits are known to 



PLATE XVIII. 




OU.E,rMOTO-llTH. 



WEED, PARSONS* C° ALBANY. 

NEPTUNE AND ITS SATELLITE. 



ELECTRO-ASTRONOMICAL ATLAS. 



05 



be retrograde, so that instead of advancing for- 
ward in their orbits from west to east aronnd their 
primary, as other satellites do, they move in the 
opposite direction. 

Q. What is known of the size of these satel- 
lites ? 

A. They have never been accurately measured, 



owing to their vast distance from the Earth, but 
were they not about three thousand miles in diam- 
eter they could not be seen. 

Q. What is known of these satellites suffering 
an eclipse ? 

A. They seldom suffer eclipses, but may suffer 
two a year. 



LESSON XLIV. 

Analysis. — Neptune — Situation — Orbit — Distance from Sun — Revolution round it — Diameter — Rate of Motion — Inclination of 
Orbit to the Ecliptic — Time on Axis unknown. One Satellite — Situation — Time around the Primary — Indication. 



Neptune. 

Neptune is invisible to the naked eye. In tele- 
scopes, it has the aspect of a star of the eighth 
magnitude. Its apparent movement is extremely 
slow ; but, as the orbit which it describes round 
the Sun is so immense, its real velocity is, never- 
theless, considerable ; it is about 12,400 miles an 
hour. 

Like all other- planets, it is sometimes nearer 
and sometimes further from the Earth. At the 
time of conjunction it is distant from us, on the 
average, 2,958,000,000 miles, whilst its minimum 
distance at opposition is less by 218,000,000 miles. 

The real dimensions are somewhat considerable, 
and in virtue of them Neptune is the third planet 
of the system. Its diameter is 37,000 miles greater 
than the diameter of the Earth. The surface of 
the globe of Neptune is more than twenty-two 
times that of the Earth, and its volume is 
nearly 105 times. 

The intensity of the heat and light received by 
that planet is but little more, at that enormous 
distance, than the thousandth part of that received 
by us. But, as nothing is known of its physical 
and atmospheric conditions or of its rotation, 
nothing can be determined on the climatic con- 
ditions of the planet. 



At a distance nearly equal to that of the Moon 
from the Earth, that is to say, about 225,000 
miles, a satellite revolves round Neptune in a 
very circular orbit, in 5 days, 21 hours, 8 min- 
utes :* this has enabled astronomers to calculate 




SATELLITE OF NEPTUNE. 



the mass of the primary. It is equal to about the 
l-17000th part of the mass of the Sun, or to 21 
times that of the Earth. Hence, the density of 
the matter of which Neptune consists is less 
than the fourth of that of the Earth, or nearly 
equal to the density of nitric acid, and a little less 
than that of sea-water. From this point of view, 



* This disc has not yet presented any perceptible trace of flattening 
neither can any spot be distinguished on it, so that the time of its rotation 
remains unknown. 



66 



ELECTRO-ASTRONOMICAL ATLAS. 



Jupiter is the planet most analogous with this 
body, whilst the force of gravity at its surface is 
about the same as on Saturn and Uranus. 
Q. "Where is the planet Neptune situated % 
A. His orbit encircles the entire solar system, 
being the ninth planet in the order of distance 
from the Sun. 
Q. What is the distance from the Sun \ 
A. It is 2,850,000,000 miles from the Sun ? 
Q. What is its diameter ? 
A. It is thirty-five thousand miles. 
Q. How long does it take this planet to per- 
form a revolution around the Sun ? 
A. It takes one hundred and sixty -six years. 
Q. What is its rate of motion % 
A. It is eleven thousand miles an hour 1 
Q. What is the inclination of its orbit to the 
Ecliptic ? 



A. It is one degree forty- six minutes and fifty 
seconds. 

Q. What is its time on its axis % 

A. Owing to its vast distance, its diurnal 
motion has not been ascertained. 

Q. How many satellites revolve around this 
planet? 

A. Only one has as yet been discovered. 

Q. How far from its primary is this satellite 
situated? 

A. It is two hundred and twenty-three thou- 
sand miles. 

Q.. In what time does this satellite revolve 
around its primary ? 

A. In five days and twenty-one hours. 

Q. What does this indicate ? 

A. The time of a lunar month on the planet. 



LESSON XLY. 

Analysis. — Comets — Where found — Appearance — Why called Comets — Appearance Varied — Distinguished from Planets ■ 

Form of Orbits — How are they distinguished. 

Comets. 

Q. What other planets are found circulating 
among the planets of the Solar System ? 

A. They are Comets. 

Q. What is their appearance ? 

A. They are bodies of the nebulous form, 
composed of a nucleus of a bright center or 
head ; the coma, a kind of envelope of a 
nebulous substance, and a tail moving in an 
opposite direction from the Sun. 

Q. Why called Comets ? 

A. They derive their name from the Greek 
word "Come," which means "hair," they resem- 
bling it in appearance, hence called Comets. 

Q. Is their appearance uniform % 




A. They are extremely varied in appearance, 



Fig. 49. 

1. TAIIXESS COMET. 2. HEAD WITHOUT TAIL OB KT70XEU8. 4 ' 

some have no tails, others have several tails, some 
appear without any nucleus. 

Q. When these bodies are far away from the 
Earth and Sun how are they distinguished from 
the planets ? 



PLATE XIX. 




WEED, PARSONS 8. CO. ALBANY, N. 



A.TOLLE.PHOTQrLITH. 



FORMS Of CO METS 



ELECTRO-ASTRONOMICAL ATLAS. 



07 



A. By the size and position of their orbits and 
the direction of their motions. 

Q. What is the form of their orbits ? 

A. They move aronnd the Sun either in ellipti- 
cal orbits or curved lines called parabolus or 
hyperbolus. 

Q. How are they to be distinguished 1 



A. Those moving in elliptical orbits belong to 
the Solar System. The others are occasional visi- 
tors, coming from far distant regions of space, 
moving around one side of the Sun, then fly away 
in paths which continue to diverge, and never 
return again. 



LESSON XLYI. 



Analysis. — Elements of Comets — Orbits — Number computed — Classes Elliptic — Long Periods — 
appeared — They are generally named after their discoverers — Size of Orbits — Comparative 
Kevolution. 



Shorter Periods — Number Re 
inclination of them — Way of 



Elements of a Comet's Orbit. 

Q. What are the elements of a Comet's orbit 

A. 1st. The longitude of the Perihelion. 2d 
The longitude of the 
Ascending Nodes. 3d. 
The inclination of the 
plane of the Ecliptic. 
4th. The eccentricity. 
5th. The direction of 
the motion. 6th. The 
Perihelion distance 
from the Sun. 

Q. The elements of 
how many Cometary 
orbits have been com- 
puted % 

A. More than two 
hundred and forty, 
and of that number 
only nineteen are 
known to be Elliptic 
and five hyperbolic. 

Q. Into how many 
classes are Elliptic 
Comets divided % 

A. In two ; those of short periods and those of 
long periods. 




Fig. 

ORBITS OI 



Q. Of these how many have re-appeared ? 
A. Of the shorter class seven have re-appeared 
and been identified and established by an entire 
correspondence of their 
elements. 

Q. Which of these is 
most distinguished % 

A. The Comet Encke; 
its period has been 
about three and a-half 
years, and eighteen 
returns have been re- 
corded. 

Q. What of the 
others % 

A. The period of 
Dedico's is five and 
a-half years ; W i n - 
necke' s five and a-half ; 
Brorsen's five and a- 
half years ; Bielas six 
and three-fifth years ; 
Donati's six and five- 
eighth years; Tarje's 
seven and a-half years. 
Q. After whom were 
these Comets named ? 
A. After the distinguished Astronomers who 
discovered them. 



50. 

' COMETS. 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. What is the comparative size of their orbits ? 

A. They are smali, all revolving within the 
orbit of Saturn. 

Q. What is the comparative inclination of 
their orbits. 



A. They are small, the average being twelve 
and a-half degrees ; the greatest thirty-one, and 
the least three degrees. 

Q. Which way do they revolve ? 

A. They revolve from west to east. 



LESSON XLVII 



Analysis. — Comparative Periods of Comets — Course of Revolution of Comets whose Orbits have been ascertained — One-half of 
them in opposite directions — Inclinations very diverse — Velocity compared with Planets in general — Far Greater — Number 
Discovered. 



Comparative Periods of Comets. 

Q. What are the comparative periods of these 
Comets ? 

A. With the exception of a few Comets whose 
periods have been computed to be about seventy- 
five years, they are considered of very long 
periods, some more than one hundred thousand 
years. 

Q. Of all the Comets whose orbits have been 
ascertained, what is the course of the revolution ? 

A. About one-half are direct, that is, they re- 
volve from west to east, and the remainder are 
retrograde. 

Q. What is said of their inclinations ? 

A. They are very diverse, some revolve within 
the zodiac and others at right angles with the 
Ecliptic. 

Q. What is their velocity in comparison to the 
planets in general ? 

A. Very much greater. The Comet of 1680 was 
880,000 miles an hour, and that of 1843, was 1,260,- 
000 miles an hour, or 350 miles per second. 

Q. How many Comets have been discovered % 



A. The number is larger, from the earliest 
period up to the present time more than eight 
hundred have been recorded, of which three hun- 
dred have their orbits computed, and of the latter 
fifty-four have been identified as returns of pre- 
vious Comets. Since optical aid has been used in 
searching for Comets, it is estimated that the 
actual number of Comets brought to view, includ- 
ing both Hemispheres, is not less than 4,000 to 
5,000. 

Q. How far from the Sun are they generally 
discovered % 

A. About 1,824,000,000 miles. 

Q. Among those Comets which have been no- 
ticed, how many passed between the Sun and 
Mercury ? 

A. There were thirty. 

Q. How many between the other respective 
orbits 1 

A. Between Mercury and Venus, forty-four ; be- 
tween Venus and the Earth, thirty-four ; between 
the Earth and Mars, twenty-three ; between Mars 
and Jupiter, six. 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON XLVIII. 

Analysis. — Celebrated Comets — Comet of 1811 — Dimensions — Aphelion distance — Halley's Comet — How distinguished — 
Appeared in many previous years — Comet of 1843 — How distinguished — Encke's Comet — Period of Return — What pecu- 
liar in its return — Donati's Comet appeared in 1858 — Effect produced — Wonder of Many — For what distinguished — Law by 
which they are Governed — Description of its Operation — Longitude of the Parhelion of the Comet 1858 — Longitude of its 
Node — Longitude of the parhelion of the Comet 1862 — Longitude of its Node — Rapidity of Comets — Cause for it. 

Celebrated Comets of the Present Century. 



Q. Among the Comets which have made their 
appearance during the present century, which are 
the most distinguished ? 

A. The one of 1811 is esteemed by Astronomers 
as a most magnificent Comet. 

Q. What were its dimensions? 

A. The head was 112,000 miles in diameter ; its 
nucleus was 400 miles. 

Q. What was the 
shape and the length 
of its tail ? 

A. Its tail was a 
beautiful fan - shape, 
extending not less than 
112,000,000 miles. 

Q. What is the 
aphelion distance of 
this Comet ? 

A. It is fourteen 
times that of Nep- 
tune, or 40, 000, 000, 000 
miles, reaching far be- 
yond the Solar System 
or the stretch of the 
largest telescope. 

Q. What is said of the Comet of 1835, commonly 
known as Halley's Comet? 

A. This is remarkable as being the first Comet 
whose period of revolution was satisfactorily 
established. 

Q. What led T)r. Halley to suspect that this 
was the reappearing of a former Comet ? 




Fig. 51. 

GKEAT COMET OF 1811, FEOM A DKAWIHO BY ADMIKAL SMYTH, IN THE 
" SPECULUM HARTWELLIA1TUM." 



A. He on examining the great Comets of 1531, 
1607, and 1682, believed they were only the reap- 
pearance of the same Comet. 

Q. What period did he fix as the time in which 
it uniformly returned ? 

A. He established the time of the interval at 
seventy-five years. 

Q. How has he con- 
vinced the world that 
he was correct in his 
conclusions ? 

A. He declared that 
the Comet would again 
make its appearance 
in the last of 1758, or 
in the beginning of 
1759. 

Q. What was the 
result of his prophecy? 
A. Gfreat interest 
was felt, and though 
he died before the 
time, yet on Christ- 
mas night, 1758, a 
peasant near Dresden 
discovered the Comet. 
Q. In looking back upon past history, have we 
reason to believe that this Comet had made its 
appearance at similar intervals before the days of 
Halley ? 

A. It was seen in England in 1066, when it was 
regarded as the forerunner of the victory of 
William of Normandy. 



70 



ELECTRO-ASTRONOMICAL ATLAS. 



Q. What then was its appearance % 

A. It was then in size equal to the full Moon, 
and in 1456 its tail reached from the Horizon to 
the Zenith. Pope Calixtus indited a prayer for 
the people as follows: "Lord save us from the 
Devil, the Turk, and the Comet." 

Q. What is regarded the earliest record given 
of this Comet ? 

A. In the 130th year before Christ. 

Q. What was said of its light ? 

A. That its light surpassed the brilliancy of the 
Sun. 

Q. For what was the Comet of 1843 distin- 
guished \ 

A. It was so intensely brilliant as to be visible 
in full daylight ; and it was so near the Sun as 
almost to graze his surface. 

Q. What period is designated as the time of the 
return of Encke' s Comet % 

A. Its period is only three and a half years. 

Q. What interesting discovery has been made 
from observations upon its motion % 

A. It returns invariably to its perihelion, two 
and a half hours earlier than the most perfect 
calculations indicate. 



Dokati's Comet. 

Q. What is said of Donati's Comet which ap- 
peared in 1858 \ +■ 

It produced great excitement and was the cause 
of universal wonder. 

Q. What was its distance from the Earth when 
first discovered \ 

A. In June of that year it was 240,000,000 miles 
and in August traces of its tail were observed 
which extended to about 50,000,000 miles in 
length. 

Q. For what other manifestations has this Comet 
been distinguished ? 



A. It has never been excelled for the brilliancy 
of its nucleus and the graceful curvature of the 
tail. 

Q. When will it return ? 

A. In about 2,000 years. 

Q. What great law controls the motion of the 
Comets 1 

A. They are controlled by the same specific 
law which governs Planets of the Solar System. 
When in their orbits thousands of millions miles 
from the Sun, they move very slow in the arc of 
an ellipse, almost immeasurable, having lost their 
charge of Coloric, they become minus. The Sun 
being positive and they deeply negative, it begins 
to exert a controlling influence over them, as that 
attraction increases continually in proportion as 
the squares of the distance decrease, they move 
swifter and swifter until, as they approach the 
Snn, they sometimes fly more than eight hundred 
thousand miles an hour. At their Perihelion 
they are very near the Sun and become very 
highly positive, and hence are propelled back 
again into fields of space with the same lightning 
speed that they were attracted toward the great 
Fount of all motion. 

Q. What is the longitude of the Perihelion of 
the Comet of 1858? 

A. It is thirty-six degrees and thirteen minutes. 

Q. What is the longitude of its Node \ 

A. It is one hundred and sixty-five degrees and 
nineteen minutes. 

Q. What is the inclination of its Angle \ 

A. Sixty-three degrees and two minutes. 

Q. What is the longitude of the Perihelion of 
the Comet of 1862 \ 

A. It is forty-nine degrees and seven minutes. 

Q. What is the longitude of its Node ? 

A. It is two hundred and seventy-eight degrees 
and fifty-eight minutes. • 



ELECTRO-ASTRONOMICAL ATLAS. 



71 



Q. What is the inclination of its orbit with the 
plane of the Ecliptic ? 

A. It is fifty-eight degrees and twenty-nine 
minutes. 




Pig. 52. 

COMET OF 1744 (CHESEATTX'S COMET), WITH MTJI/nPLE TAILS. 

It is right to say that among the numerous 
comets observed up to the present time, either 
with the naked eye, or by means of telescopes, 
the majority are distinguished by a nebulosity 
surrounding the nucleus, and a great number, 
especially of the most brilliant ones, possess a 
luminous train or tail. With others, the tail, 
displayed fan-like, is divided into many branches, 
as if the body had in reality several distinct tails. 
Fig. 52 gives an idea of the varied forms of these 
cometary appendages. 

This diversity of aspect will, perhaps, some 
day, enable astronomers to class comets into gen- 
era, species and varieties, and will doubtless 
facilitate the perfection of the theory of the phe- 



* Note. As we go to press, a new Comet is announced, discovered first at Marseilles, Prance, April 17, by Mons. Coggia, and recently < 
by Prof. Swift of Rochester, N. Y. Although its direction is represented as earth-ward, yet no fears are entertained of a collision, for the elec- 
trical law of radiation is sufficient to prevent it. Reference as to location, may be had to Map 1 of the Star Sketches in this Atlas, page 75. 



nomena which these bodies present, which is still 
so obscure. 

Comets, as we have said, form part of our Solar 
System. Like the planets, they revolve round the 
Sun, traversing with very variable velocities ex- 
tremely elongated orbits ; the form of the comet- 
ary orbits furnishes us with the first of their 
specific characters. * 

Q. Why do Comets pass out of sight so rapidly 
after passing their Perihelion ? 

A. They move around the Sun in orbits much 
more elongated than that of the Earth and when 
they cross the plane of the orbit of the Earth on 
their flight to regions of space, they are then mov- 
ing in one direction and the Earth in another, and 
as the Earth moves at the rate of sixty-eight 
thousand miles an hour and the Comets at the 
rate of a million miles an hour, they seem to move 
much faster as they soon disappear, while their 
motion is slower and slower till they arrive at 
their Aphelion point. 

Q. What may be considered a remarkable fact 
in respect to Comets ? 

A. That the real diameter of their nebulosity 
increases proportionally as they become more dis- 
tant from the Sun, and the nearer they come, the 
smaller the nucleus but the more brilliant. 

Q. What forms the ground work of all our cal- 
culations respecting the distances of all celestial 
orbs? 

A. The semi-diameter of the Earth. 

Q. What is necessary or sufficient to enable a 
person to understand the mode by which the dis- 
tances of the heavenly bodies are determined ? 

A. A slight knowledge of Geometry and Trigo- 
nometry. 



72 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON XLIX. 

Analysis. — What supposed to be — How produced — What called — Why so called — How many seen in an Hour — Showers of 
Stars — When exhibited — At what Intervals — Hombold and Bompland's Observations — Arago's Observations — Regular 
Periods of Showers — Intersection of the Earth and the Orbit of the Comet — Brilliant display accounted for — Light produced 
by their rapid flight through the Atmosphere — Annual Exhibition of Meteors in August — Regularity accounted for — 
Schiaparrelli's discovery. 



Meteors, Shooting Stars or Aerolites. 

In the immense number of meteors which invade 
the regions of the air in a year, there are some per- 
haps that only pass through its domain and 
continue their path in space, after having presented 
us with the spectacle of a transient illumination. 
A great number, on the other hand, not only do 
not again leave our atmosphere, being vaporised 
therein, but, when of large size, attain the very 
surface of the Earth. Falls of stones, ferruginous 
masses, and dust, from the upper regions of the 
air, are proofs of this assertion. 

From shooting stars to meteors, or bolides, the 
transition in our narrative is easy : the difference 
between these two orders of phenomena is not 
very strongly marked. 

Bolides are luminous bodies of circular, or 
rather of spherical, form, and of sensible apparent 
diameter. Like shooting stars, they appear sud- 
denly, but generally they move more slowly, and 
disappear after some seconds. Their light is 
ordinarily less vivid, but their much more con- 
siderable apparent dimensions are sufficient to 
compensate this difference of intensity. The 
illumination of the landscape by the presence of 
a meteor sometimes approaches that of moonlight. 
Most of them leave behind a luminous train ; 
others explode with violence, and sometimes the 
explosion is accompanied with reports like dis- 
charges of artillery. 

The appearance of meteors is more rare than 
that of shooting stars, the total number of obser- 
vations recorded amounting at most to a thousand, 
reckoning those recorded by the ancients. 



A curious circumstance, and one which helps 
to prove the relationship between the shooting 
stars and meteors, is the fact that the appearances 
of meteors are more frequent in August and 
November than at other epochs of the year ; and 
the total number from July to December exceeds 
also that observed from December to July. 




APPEARANCE OF A METEOR IN A TELESCOPE. (SCHMIDT.) 



[One of the most curious observations of a 
meteor which have been recorded, leaving that of 
1783 out of the question, was recently made by 
Dr. Schmidt, who was fortunate enough to observe 
a large meteor in a telescope, under a magnifving 
power of eight times. The fire-ball was twin, and 
was followed by several smaller ones, following 
side by side with parallel motions of translation 
until all were extinguished (fig. 53). This obser- 
vation lends force to the supposition that meteors 
exist in space as a crowd of bodies, revolving 
round each other, before they enter our atmos- 
phere.] 

Q. What are they supposed to be, and how are 
they produced % 

A. Of metallic substances similar in composition 
to the Comets themselves accompanying them in 
their revolutions around the Sun, as cosmical 
clouds or meteoric swarms. 



ELECTRO-ASTRONOMICAL ATLAS. 



73 



Q. Why called Shooting or Falling Stars 1 

A. Because of their rapid motion in darting 
through the heavens. 

Q. How many may be observed in ordinary 
times in the interval of an hour ? 

A. From ten to twenty may be seen. 

Q. At what periods of 
time does the shower of 
Stars exhibited on the 
12th and 13th of Novem- 
ber occur ? 

A. At intervals of 
thirty-three years. 

Q. What evidence 
have we of this pheno- 
menon ? 

A. Homboldt and 
Bompland observed on 
the 12th and 13th of 
November, 1799, a 
shower of Stars, as a real 
rain of fire. 

Q. In what following 
year did it recur in great 
force ? 

A. In the year 1833, 
November 12th, Arago 
compared the shower to 
a fall of snow. 

Q. When did the last 
periodic shower occur % 

A. It was again observed on the 14th of No- 
vember, 1867. 

Q. How is the regularity of these seasons ac- 
counted for or determined % 

A. On the principle of the regularity of the 
revolution of the Earth, and the intersection of its 
orbit by the passage of the meteoric shower when 
the Earth is passing through the cloud or very 
near it at the time of the periods above mentioned. 




Q. How can you account for the brilliant dis- 
play of light exhibited in their passing through 
the heavens \ 

A. Their light seems to be produced by their 

rapid flight through the atmosphere, causing 

their ignition by the compression of the air and 

their consumption in 

their passage. 

Q. What are we to 
understand respecting 
the meteors annually 
exhibited on the 10th of 
August ? 

A. The August Mete- 
ors annually revealed to 
us are produced by their 
annual revolution inter- 
secting the Earth' s orbit 
on the 10th of August. 

Q. What reason have 
we to conclude that this 
ring of meteoric stones 
represents the orbit of a 
previous Comet ? 

A. Schiaparelli has in 
fact discovered so close 
a resemblance between 
the path of the August 
meteors and that of the 
Comet 1862, No. 3, that 
there cannot be any 



Fig. 54. 



AUGUST AND NOVEMBER METEOR-SHOWERS. (ORBITS OP 

comets in., 1862, and I., 1866.) 



doubt as to their complete identity. 



The calculations of Schiaparelli, Oppolzer, 
Peters, and Le Verrier, have also discovered the 
comet producing the meteors of the November 
shower, and have found it in the small comet of 
1866, No. I., first observed by Tempel, of Mar- 
seilles. Its transformation into a ring of meteors 
has not proceeded nearly so far as that of the 



74 



ELECTRO-ASTRONOMICAL ATLAS. 



comet of 1862, No. III. Its existence is of a much, 
more recent date ; and, therefore, the dispersion of 
the meteoric particles along the orbit, and the 
consequent formation of the ring, is but slightly 
developed. 

According to Le Verrier, a cosmical nebulous 
cloud entered our system in January, A. D. 126, 
and passed so near the planet Uranus as to be 
brought by its attraction into an elliptic orbit 
round the Sun. This orbit is the same as that of 
the comet discovered by Tempel, and calculated 
by Oppolzer, and is identical with that in which 
the November group of meteors make their revo- 
lution. 

Since that time, this cosmical cloud, in the form 
of a comet, has completed fifty-two revolutions 
round the sun, without its existence being other- 
wise made known than by the loss of an immense 
number of its components, in the form of shooting- 
stars, as it crossed the Earth' s path in each revolu- 
tion, or in the month of November, in every 33 
years. It was only in its last revolution, in the 
year 1866, that this meteoric cloud, now forming 



part of our solar system, was first seen as a comet. 
The orbit of this comet is much smaller than 
that of the August meteors, extending at the 
aphelion as far as the orbit of Uranus, while the 
perihelion is nearly as far from the Sun as our 
Earth. The comet completes its revolution in 
about 33 years and 3 months, and encounters 
the Earth's orbit as it is approaching the Sun 
toward the end of September. It is followed by 
a large group of small meteoric bodies, which 
form a very broad and long tail, through which 
the Earth passes on the 13th of November. Those 
particles which come in contact with the Earth, or 
approach so near as to be attracted into its atmos- 
phere, become ignited, and appear as falling stars. 
As the Earth encounters the comet's tail, or 
meteoric shower, for three successive years at the 
same place, we must conclude the comet' s track 
to have the enormous length of 1,772,000,000 
miles. In Fig. 54, C D represents a portion of the 
orbit of this comet which is identical with the 
orbit of the November meteors. — Spectrum 
Analysis. 



LESSON L. 

Analysis. — Remarks — Constellations — Design in presenting- an Elementary Work — Not Extensive or Critical — In considering the 
Stellar Universe — The Object in Presenting Constellations — How differ from Planets — In Twinkling and Scintillating — 
Description of a few — Exhibited in the Northern Sky — The best time of observing them — What Called — Why Called Northern 
Circumpolar — North Pole point of Revolution — Consideration of Maps —MAP I. — Constellation Great Bear, Ursa Major — Time 
of appearance — Number of Stars contained in the Group — Figure formed Large Dipper — Two Northern Stars Pointers— Why 
called thus — Polaris the object to which they point — Revolution — 2d Constellation — Little Bear — How Distinguished — Con- 
tains Polaris— North Pole Star — A Fixed Star — Why called Fixed Stars — They revolve in the Universe — Great Velocity — Time 
its Light travels down to us — 3d Constellation — Gasdopia —Location —Form of Figure —Sprawling " W " — Cepheus and Draco 
— Where Located — Nothing Striking — Perceus elsewhere. 



Constellations. 

Remarks. — It is not my design in this Element- 
ary Work to be very extensive or critical in what 
may be presented of the Stellar Universe. 

In studying the stars, that we may the more 
easily comprehend their location in the heavens, 



they have been arranged in groups, called Constel- 
lations. 

We will now present some of these Constella- 
tions, and describe a few of the principal stars 
contained in them, as exhibited in our northern 
sky, with the best time for looking at them. 



ELECTRO-ASTRONOMICAL ATLAS. 75 


Q. How do they differ in appearance from the 


A. Because they point out and are always in 


planets ? 


range with a bright star called Polaris. 


A. They twinkle or scintillate, and no telescope 


Q. How often does the dipper revolve around 


has been able to enlarge them into a disc. 


this star ? 


Q. AA r hat are these constellations called ? 


A. Once in twenty-four hours, never sinking 


A. They are called Northern Circnmpolar and 


below the horizon. 


Southern Constellations. 


Q. What other constellations are revealed on 


Q. Why called Northern Circumpolar ? 


this map ? 


A. Because they revolve around the north polar 


A. Little Bear and Cassiopia. 


star, recognized on map I, as Polaris. 
Q. In considering the following Star Maps, how 




Little Bear, or Ursa Minor. 


are their points of the compass arranged. 


Q. For what is this constellation distinguished ? 


A. The right hand west, the left hand east, the 


A. Its form is that of a little dipper, containing 


top of map north and the bottom south. 


seven stars, one of them distinguished as the Pole 
Star, called Polaris. 




MAP I. 


Q. Why called the Pole Star? 


Constellation The Great Bear, — Ursa 


A. It is esteemed the point of the northern pole 


Major. 


of the Earth. 


Q. What time of the 


MAI 


?i. 


Q. To what import- 


year are the constel- 






ant class of stars does 


lations on this map 


|QH m^| 




Polaris belong ? 


most clearly revealed? 






A. To those called 


A. About the first 






Fixed Stars or Suns. 


of November, at nine 


^3Jt0 




Q. Why are they 


o'clock in the even- 




1 


called Fixed Stars or 


ing, in our latitude, 




■Bflj h 


Suns? 


they are visible every 




Hfl 


A. Because they 


night. 


HHSSHHHPwSli 




have appeared for 


Q. How many stars 






ages to occupy the 


in this constellation 




^H 


same place. 


are visible to the 




^fi^lBKfty^^J 


Q. Do they not re- 


naked eye ? 






volve in their orbits 


A. There are one 


Pig 


55. 


like the planets ? 


hundred and thirty-eight. 


A. Their rate of motion is far greater than that 


Q. How are the seven principal stars arranged ? 


of many of the planets. 


A. They appear in the form of a Large Dipper. 


Q. What is the rate of motion of Polaris ? 


Q. What are the two extreme northern stars in 


A. It is ninety miles per minute. 


the cup called ? 


Q. How long does it take its light to reach the 


A. They are called pointers. 


Earth % 


Q. Why are they so called ? 


A. It takes fifty years. 



76 ELECTRO-ASTRONOMICAL ATLAS. 


Q. How many stars are visible in this constella- 


A. They are arranged somewhat like a broken- 


tion? 


backed chair, or a sprawling capital W. 


A. There are twenty -seven. 


Q. What other constellations are found on this 
map? 




Constellation — Cassiopia. 


A. Cepheus and Draco are located nearly south 


Q. Where is this constellation located on the 


of Polaris. 


map? 


Q. Is there any thing striking in their features ? 


A. Nearly east of Polaris. 


A. There is nothing, and Perseus is better 


Q. What is the form in which the principal 


represented on another map. 


stars are grouped. 




LESSON LI. 


Constellation Orion. 


Analysis. MAP II — Time of favorable appearance — Names of the Constellations — Distinguished — The most beautiful 


Constellation in the Sky — Whale better seen elsewhere — Stars of Belt of Orion — The Bull or Taurus — Situation — How 


Marked — Cluster called Hyades — Another cluster called Pleiades — Another Constellation called Gemini, or the Twins — Where 


Situated — Names of the most important Stars — Castor and Pollux — Little Dog — Location — How distinguished — Procyon 


and Gomelza — Great Dog — Situation — Name of the largest — Sirius Brightest Star — Rate of Motion — Time it takes to reach 


the Earth — Distance estimated — Diameter — Constellation The Whale — Situation. 


MAP II. 


A. There are three stars in a line, near the cen- 


Q. What time of year may the constellations on 


ter of the parallelogram, called the belt of Orion. 


this map be most easily pointed out ? 










A. About the first 


map n. 


Bull, ok Taurus. 


of February, at nine 




Q. Where is the 


o' clock in the evening. 




group called the Bull, 


Q. What are the 


HjM B9 


situated ? 


names of the constel- 




A. It is in the north- 


lations on this map ? 




west, and marked by 


A. Orion, Bull, 


^1 IMM RQ 


a V shaped cluster, 


Twins, Great Dog, 




called Hyades. 


Little Dog, and the 




Q. What cluster of 


Whale. 




stars is found near it ? 


Q. For what is 




A. A group of seven 


Orion distinguished ? 




stars may be found 


A. It is the most 


|^BBHflHH3BiiB|fa"iK 


north-west of Bull, 


beautiful constella- 




called Pleiades. 


tion in the sky. 


Fig. 56. 


Q. Where can the 


Q. How many stars form the belt of Orion and J constellation Geminii or the Twins be found ? 


where are they located % ' A. North-east of Orion, at this time. 



ELECTRO-ASTRONOMICAL ATLAS. 



77 



Q. How is it marked, or what is its shape 1 

A. It is marked by a large quadrilateral of 
stars. 

Q. What are the names of the most important 
stars in this group ? 

A. They are Castor and Pollux, the most north- 
ern and brightest stars of the group. 



Little Dog. 
Where is the location of the Little Dog ? 
It is situated east of Orion. 
How is it distinguished ? 
It is marked by two solitary stars, Procyon 



and Gromelza. 



The Great Dog. 

Q. How is this constellation marked and where 
located ? 

A. It is a group of several stars, located south- 
east of Orion. 

Q. What is the name of the largest star and for 



what is it distinguished % 

A. It is called Sirius, and is the largest star in 
the whole heavens. 



Sirius. 

Q. What is the rate of motion of Sirius ! 

A. It is eight hundred and forty miles per, 
minute. 

Q. How long does it take the light to reach the 
Earth ? 

A. It takes twenty-two years. 

Q. What is its estimated distance from the 
Earth \ 

A. It is said to be 3,375,000 times that of the 
Sun from us. 

Q. What is its diameter ? 

Q. Twelve millions miles in diameter. 



The Whale. 
Q. Where is he situated ? 
A. He is located north-west of Orion. 



LESSON LII. 
Constellation Yirgo. 

Analysis. — MAP III — Favorable time for Inspection — When seen in the Heavens — How known — Large Constellation — One 
Star of first Magnitude — Spica its name — Leo, or the Lion — Where situated — How easily known — Shaped like a Sickle — 
An inverted figure 5 — Regulus the largest — On the Ecliptic — Gamma — Where situated — 3d Constellation — Hydra — 
Situation — Form of Serpent Swimming from East to West — Stars small. 



MAP III. 
Virgo. 

Q. At what time is 
this constellation 
more clearly seen % 

A. On the first of 
April, at nine o'clock 
in the evening. 

Q. Where in the 
heavens may it be seen 
at this time ? 

A. Near the Mer- 
idian. 

Q. How may it be 
known ? 



MAP III. 




A. It is a large 
constellation, with 
one star of the first 
magnitude, called 
Spica ; the others are 
not easily traced with- 
out a Plenisphere. 



Leo, or the Lion. 

Q. Where situated* 

A. Just west of 
Virgo. 

Q. How is it easily 
recognized ? 

A. By six stars, 



78 



ELECTBO-ASTRONOMICAL ATLAS. 



shaped like a sickle or an inverted fig- 
ure 5. 

Q. Which of these stars is the brightest, and 
where situated? 

A. It is a star called Regulus, and is on the 
Ecliptic. 

Q. What is the next important star in this group 
and where located % 

A. It is Gramma, and is generally situated near 



the radient point of the November meteoric 
shower. 



Constellation Hydka. 
Q. Where situated % 
A. It is located south of Leo and Virgo. 
Q. What is its form, course and size of the stars % 
A. It is the form of a serpent, swimming from 
east to west, and its stars are small. 



LESSON LIII. 
Constellation Bootes. 

Analysis. — MAP IV — Time of Appearance — In June — Situation in the Heavens — The Brightest Star Arcturus — Where found 
— On Meridian — Shape Parallelogram — Four bright Stars — Form — Coffin — Another group East — Like a boy's cap — Northern 
Crown — Large Constellation further East — Hercules — Size — What figure — Two Quadrilaterals — Opinion respecting the 
course of the Solar System — Drifting toward Hercules. 



MAP IV. 

Constellation Bootes. 

Q. What is the time of its appearance % 

A. In the month of June, nine o'clock, p. m. 

Q. Where in the 
heavens may this con- 
stellation be found at 
this time \ 

A. It may be seen 
on the meridian, 
south-east of the 
Great Bear. 

Q. What is the 
name of its largest 
star? 

A. It is called Arc- 
turus. 

Q. AVhere in the 
heavens may it be 
found at this time % Fi > 

A. Facing the south, you will see it on the 
meridian, and in shape like a parallelogram, of 
four bright stars. 







MAP IV. 














BK2^S£ 


WR 




99 




j^KH^y 


^^■mhj 








SB*] 


jCT 



Q. What form does this group of stars represent? 
A. They form a figure somewhat similar to a 
coflin. 

Q. What group of stars is found east of Bootes % 
A. A semi-circle of 
stars, like a boy's cap, 
called the Northern 
Crown. 

Q. What large con- 
stellation may be 
found further east % 

A. It is called Her- 
cules. 

Q. What is the size 

of the stars and what 

figure do they form % 

A. They are small 

and present the figure 

of two quadrilaterals. 

»• Q. What is the 

present opinion entertained as to the course the 

Solar System is now taking % 

A. It is supposed to be drifting toward Hercules. 



ELECTRO-ASTRONOMICAL ATLAS. 79 


LESSON LIV. 


Constellation The Swan. 


Analysis. — MAP V — Time favorable —Where found — Overhead — Figure formed — Large Cross — Principal Star at foot — 


Albireo— Multiple Star — The Eagle — Where situated — South of Swan — How distinguished— A Large Star— Atair — 


Pegasus— Where located — North-east of Eagle— Figure of these Stars — Perfect Square — The most Western found— Head 


of Andromedia — The Lyra — Where situated — West of Swan and North-west of Eagle — What Star Prominent — Vega — 


What completes the group — Four faint Stars. 


map y. 


Pegasus. 


Constellation The Swan. 


Q. Which way from the Swan is this group 


Q. What time in the year does this constellation 


located? 


make its appearance ? 


A. It is situated directly east of the Swan, and 


A. On the first of September, 9 o'clock in the 


north-east of the Eagle. 


evening. 


Q. What is the figure represented by these stars ? 


Q. Where can the Swan be found at this time ? 


A. A perfect square is formed by four of the 


A. Overhead, in the map v. principal stars. 


Milky Way. 




VJ. wnere is tne 


Q. What is the fig- 




most western one 


ure formed by the 




found ? 


stars of this constella- 




A. It is located in 


tion. 




the head of Andro- 


A. They are so ar- 
ranged as to form a 


^^H 


media. 


The Lyra. 


large cross. 




Q. Where is this 


Q. What is the 


■H 


constellation situ- 


name of the principal 


Mfaj h 


ated? 


star at the foot ? 




A. It is found lo- 


A. It is called Al- 




cated west of the 


bireo, a multiple star. 




Swan <*r\i\ nrvrt. n.-cp-oof 




Pi e- »• of the Eagle. 




The Eagle. 


Q. What distinguished star is found in this 


Q. Where is it situated? 


constellation ? 


A. Nearly south from the Swan. 


A. There is a very bright star called Vega. 


Q. How is this constellation distinguished ? 


Q. What other stars complete the group ? 


A. It is marked by a very large star called 


A. Just below Vega are four faint stars, form- 


Atair, and several small ones. 


ing an oblique parallelogram. 



ELECTRO-ASTRONOMICAL ATLAS. 



LESSON LV. 

Constellation Perseus. 



Analysis. — MAP VI — When favorably seen— December — Where found — Meridian — Well North in Milky Way — Figure of 
chief Star — Turkish Sword — Bent at the point — What near the point — Mass of Telescopic Stars, very beautiful — One marked 
— Called Algol — Constellation Aries or Bam — Where seen — South of Perseus — Figure formed of Principal Star — Eight. 
Angled Triangle — Point in the Seasons marked — Vernal Equinox — What Constellation South of the Ram — Whale — Figure 
easily traced — Pentigon of Stars. 



MAP VI. 

Constellation Perseus. 

Q. What time is most favorable for its exhibi 
tion? 

A. In the month of December, 9 o'clock P. m. 

Q. Where then can 
it be found ? 

A. On the meridian, 
well to the north, in 
the Milky Way. 

Q. What is said of 
the chief stars in this 
constellation ? 

A. They are not 
very bright, but they 
form the figure of a 
Turkish sword, much 
bent at the point. 

Q. What is dis- 
covered near the point 
of the sword? 

A. There is a mass of telescopic stars, the most 
beautiful, perhaps, in the sky. 

Q. What one is found near this group which is 
rather a marked star. 



A. It is called Algol, distinguished as a strange, 
variable star. 




Constellation Aries, or The Ram. 
Where is this seen ? 

A. It is discovered 
south of Perseus. 

Q. What kind of a 
figure is formed by 
the principal stars? 

A. It forms a right- 
angled triangle. 

Q. What point in 
the Seasons is marked 
by this constellation ? 
A. Long ago it has 
been known to mark 
the place of the Ver- 
nal Equinox. 

Q. What very large 
yet indistinct constel- 
lation is found south of the Ram ? 
A. It is the Whale. 
Q. What figure is easily traced in it? 
A. There is clearly seen one pentigon of stars. 



ELECTRO-ASTRONOMICAL ATLAS. 



SI 



LESSON LYI. 

CONTRAST OF THE DISTANCE OF THE SUN AND THAT OF THE Fixed Stars 

From the Earth. 

Analysis. — Remarks. — Rate of motion of ball from an Armstrong gun — Time taken to reach the Sun — Time for the sound of the 
Explosion to reach the Sun — Prof. Mendenhall on nervous sensation — The infant burns its finger by touching the Sun — Time 
necessary to realizing, the sensation — Earth on disc of Sun — Require a large telescope to discover it — Distance of Sun from 
Earth compared to that of the Fixed Stars — The Fixed Stars, Suns — Do not remain unmoved — Revolve in the Universe like 
other Planets — Principal Suns named — Why appear small — Distance cannot be computed by miles — Velocity of light consid- 
ered — Miles per second — Number in 24 hours — At this rate how long to reach the nearest Fixed Star — 61 Gygni — Vega — 
Sirius — Ursce Majoris — Arcturus — Polaris and Cappella — These do not shine by reflection — Suns in other Systems. 



On the Distance of the Sun. 

Remark. — Reflection only can bring to our 
minds an adequate idea of the immense distance 
which exists between us and the Sun. 

Q. What is the rate of motion of a ball fired 
from an Armstrong gun % 

A. It is four hundred yards per second. 

Q. At this rate, how long will it take for it to 
reach the Sun % 

A. It will take thirteen years. 

Q. How much longer before the sound of the 
explosion would reach the Sun ? 

A. Six months later. 

Q. Which travels the faster, sound or nervous 
sensation % 

A. Prof. Mendenhall says, sensation upon the 
nerves travels ten times slower than sound. 

Q. If, therefore, an infant were born, with an 
arm of the somewhat inconvenient length of 91,- 
500,000 miles, so as to reach the Sun, and should 
he stretch out his arm, touch the Sun, and burn 
his finger, how long before he would feel the 
sensation % 

A. That child must live till it has grown to man- 
hood, and reaches the age of 135 years, before he 
will be conscious of the fact that the tip of his 
finger was burned. 

Q. Suppose the Earth be placed on the disc of 
the Sun, could it be seen with the naked eye ? 

A. It would require the aid of a large telescope 
to make it visible. 



Q. With all this disparity of the size and. dis- 
tance of the Sun from the Earth, how much greater 
the size and distance from the Earth is one, even 
the nearest of what are termed Fixed Stars % 

A. We can only answer this question by com- 
parison — hence, call your attention to the follow- 
ing in respect to what is said of the Fixed Stars. 



Fixed Stars. 

Q. What are they? 

A. They are called Suns. 

Q. Why Fixed Stars % 

A. They appear always to occupy the same 
place in the heavens. 

Q. Do they remain unmoved as Fixed Stars % 

A. They revolve in their respective orbits in the 
Universe, like other planets. 

Q. Can you name the principal Fixed Stars % 

A. Alpha Centauri, 61 Cygni, Vega, Sirius, 
Ursse Majoris, Arcturus, Polaris, Capella. 

Q. Why are they so small % 

A. They are so far from us. 

Q. How far off is the nearest ? 

A. So far it is impossible to compute its distance 
by miles. 

Q. How can we obtain an adequate idea of its 
distance from the Earth ? 

A. Something of an idea may be gained of the 
distance if we consider the rapidity with which 
light travels. 

Q. What then is the velocity of light ? 



ELECTRO-ASTRONOMICAL ATLAS. 



A. It is one hundred and ninety-two thousand 
miles per second. 

Q. How many seconds are contained in twenty- 
four hours ? 

A. Eighty-six thousand and four hundred. 

Q. According to this basis of reckoning, how far 
will light travel in twenty-four hours % 

A. It will traverse sixteen billions live hundred 
and eighty-eight millions eight hundred thousand 
miles. 

Q. At this rate, how many days will it take the 
light of the nearest fixed star to reach us ? 

A. It must continue its course at this tremendous 
velocity thirteen hundred days, or over three and 
a-half years, before a glimpse of it can be obtained 
by any of the inhabitants of the Earth. 

Q. If this incomprehensible distance lies between 
us and the nearest Fixed Star, what must be that 
lying between the Earth and the most distant % 

A. In answer, we will give the number of years 
required by light to travel the different distances 
of other fixed stars : 

1. Alpha Centauri, three years and six months. 



2. 61 Cygni, nine years and four months. 

3. Vega, twenty-one years. 

4. Sirius, twenty-two years. 

5. Ursse Majoris, twenty-two years. 

6. Arcturus, twenty- six years. 

7. Capella, seventy-two years, or 390,541,824,- 
000,000 miles. 



Polaris. 

8. Polaris, fifty years, or 271,209,600,000,000 
miles. 
. Q. What is the rate of motion of Polaris ? 

A. It is ninety miles per minute. 

Q. How long does it take its light to reach the 
earth ? 

A. It takes fifty years to travel down to us. 

Q. Do you perceive the utter impossibility that 
these stars shine by reflected light % 

A. It is evident that they are Suns — each of 
them is a focus of light and heat, and probably 
the center of a system comprising, like ours, 
planets, satellites and comets. 



LESSON LVII. 
Light. 

Analysis. — What is it — Views of Sir Isaac Newton — Flowing out from the " Orb of Day " — Recuperation, or Waste Away — Space 
embraced in Solar System — Rapidity of light — At this rate how long will it take to fill the Space — Does not remain Stationary 
— Moves on in Circle — Light changes its Polarity — Is received back to the Sun — How does the Sun remain undiminished and 
brilliant as ever — By recuperation in the return of it to the Sun — No indication of a continued work of creation — Principle 
illustrated by. 



Q. What is light ? 

A. It is an electrical effusion of brilliant parti- 
cles or bright scintillations emanating from the Sun. 

Q. What was the theory of Sir Isaac Newton 
respecting the origin of light % 

A. That light is an emanation of inconceivably 
minute particles flying off from the body of the 



Sun through that space which is occupied by 
those opaque bodies which are governed by its 
influence. 

Q. If light be an emanation of infinitesimal 
atoms, or particles of matter flowing out from the 
"Orb of day," why is it not diminished and 
wasted away ? 



ELECTRO-ASTRONOMICAL ATLAS. 



83 



A. This could not fail to be manifest if there 
was not a constant recuperation or increase of the 
original fountain. 

Q. To what extent does light emanate from the 
Sun? 

A. It is an acknowledged and well-authenticated 
fact in science, that light radiates in every direc- 
tion from this central luminary, filling the entire 
space occupied by the Solar System. 

Q. How many miles of space are embraced in 
the Solar System ? 

A. Not less than seventeen billions one.hundred 
million miles. 

Q. What is the velocity of light ? 

A. Light travels at the rate of one hundred and 
ninety-two thousand miles in a second. 

Q. At this rate, how long will it take to fill the 
vast and almost infinite space described above, 
with light \ 

A. It will take about four hours. 

Q. When this vast expanse is once filled with 
this ocean of light, does it continue to occupy this 
immense space ? 

A. Overflowing light is one of the forms in 
which the element of the Sun, electricity, is mani- 
fested throughout the Solar System. 

Q. What peculiar course does electricity pursue 
when it flows out from the Sun ? 

A. Electricity always runs in a circle, hence 
returns to its original fountain. 

Q. What conclusion must necessarily be drawn 
in respect to the course taken by light ? 

A. That light being an exhibition of one of the 
forms of electricity, it must in like manner flow in 
a circle, and again return to the place whence it 
emanated. 

Q. Do you ask how light can return to the Sun ? 

A. It was thrown out by the positive force of 
the Sun, and having changed its polarity it is at- 
tracted and received back to the Sun. 



Q. Are we then to understand that the great 
ocean of light, filling the entire Solar System, 
passes on and gives place to another % 

A. On this principle the vast ocean of light 
must give place and the space be filled by another, 
every four hours, then displaced and filled again 
in the same short space of time, and so on, in 
endless succession. 

Q. What must have been the inevitable result, 
if light be the emanation of infinitesimal effusions 
from the Sun, unsupplied from some source ? 

A. The Sun long since would have frittered 
away and been utterly annihilated by waste. 

Q. How then has it remained undiminished and 
as brilliant as ever ? 

A. Evidently this waste must be supplied either 
by the return, in some imperceptible manner, of 
these particles to their original source, or that the 
Sun, the great fountain of light, be constantly fed 
by creative agency exerted upon it. 

Q. If the latter conclusion be entertained, what 
principle in the order of creation would be vio- 
lated? 

A. From the order of creation we learn that all 
things were created in a limited time, hence, no 
indication is given of a continued work of creation. 

Q. What may be regarded the most reliable and 
correct position to be occupied in this matter ? 

A. We are, from full evidence, inclined to the 
former position, and in sustaining it, present the 
fact that light is only the ever-flowing scintillations 
of electricity, and, like it, necessarily runs in a 
circle; hence, having accomplished its mission, 
returns, like all electrical currents, to its original 
fountain, the Sun. 

Q. What beautifully illustrates this principle 
of action ? 

A. The ocean, by evaporation, supplies the 
clouds with water, this is borne over the globe, 
and discharged among the mountainous regions to 



84 



ELECTRO-ASTRONOMICAL ATLAS. 



supply the high lakes and fountains, these, in re- 
turn, send forth the little rills and streams, which, 
meeting in their course, form rivers, which empty 



into the ocean again, and keep that immense 
reservoir from becoming exhausted. 



LESSON LVIII. 
Attraction of Gravitation. 

Analysis. — Attraction of Gravitation defined — Seen in the power the Sun exerts over the Planets — All under the magnetic 
influence of the Sun — Planets rendered Magnets by the electrical power of the Sun — This inherent magnetism controls the 
Satellites — This magnetism called Terrestrial Magnetism — Subject Terrestrial Magnetism or the Magnetism of the Earth — This 
magnetism accounted for — Sun a great Galvanic Reservoir — Heat of Torrid Zone — Compared with Temperate and Frigid Zone 
— Intensity of the heat of the Sun — Three hundred times greater than any point on the Earth's surface — Sir John Herschell's 
Note. 

Terrestrial Magnetism, or the Magnetism 
of the Earth. 

Q. How is terrestrial magnetism accounted for 1 

A. Upon the theory that the Sun, being the 
great Gfalvanic reservoir, pours its streams of light 
and heat vertically upon the space embracing 
forty-seven degrees of the Earth' s middle regions, 
or twenty -three and a-half degrees each side of the 
equator, constituting the torrid zone. 

Q. What is the heat of the torrid zone when 
compared with the temperate or frigid zones ? 

A. Far greater, and always uniform and ex- 
cessive. 

Q. What is supposed to be the intensity of the 
heat at the surface of the Sun ? 

A. It has been estimated to be three hundred 
times that received at any point of the Earth' s sur- 
face. 

Q. What estimate did Sir John Herschell place 
upon the heat of the Sun ? 

A. He supposed that it would be sufficient to 
melt a cylinder of ice forty-five miles in diameter, 
plunged into the Sun, at the rate of two hundred 
thousand miles a second. 

Note. — This estimate being correct, we are not 

surprised that the entire planetary system is under 

called which is the electrical control of this great Gfalvanic Battery, 

and, as a consequence, revolve in their respective 

spheres, accomplishing the will of their Creator. 



Q. What is the attraction of gravitation % 

A. It is the magnetic influence which one body 
has over another in attracting it to itself. 

Q. How is this manifest in the planetary system % 

A. It is seen in the power exerted by the Sun 
over the planets, and in the controlling power of 
these over their satellites. 

Q. How do the planets receive their magnetic 
influence \ 

A. They receive it from the Sun. 

Q. Are all bodies, more or less, under the influ- 
ence of magnetism ? 

A. All the heavenly bodies in the Solar System 
are more or less under the influence of this magic 
power. 

Q. How do they receive their magnetic influence 
from the Sun % 

A. The Sun is a great Galvanic Battery, and, by 
its electrical power, renders the Earth and every 
planet a magnet. 

Q. What is the influence these planets exert 
upon their satellites and other bodies surround- 
ing them ? 

A. This inherent magnetism of the planet con- 
trols its satellites and every thing else within the 
scope of its influence. 

Q. What is this magnetism 
manifest in the Earth % 

A. It is called terrestrial magnetism. 



ELECTRO-ASTRONOMICAL ATLAS. 






LESSON LIX. 
Terrestrial Magnetism — Continued. 

Analysis. — Torrid regions — More deeply electrified — Result — They are positive — Polar negative — Reasons for this — Effect 
produced upon the Earth — Earth filled with electricity becomes a magnet — This Terrestrial Magnetism seeks and flows out of 
the Magnetic Poles — Points of the greatest cold — Both North and South — Result — Consequence of the combined action of 
these forces — Explanation — Effect of these currents on the Needle — Magnetic Poles and Geographic not the same — At the 
Geographic no effect on the needle — Reasons why — Note. 



Q. What is the consequence of those torrid 
regions being more directly under the influence of 
the Sun's rays ? 

A. Those regions become more deeply electrified 
than either the temperate or frigid zone. 

Q. What other results necessarily follow ? 

A. The equatorial regions are positive, while 
the polar regions are comparatively negative. 

Q. What reasons can be given for this ? 

A. The first reason is, that the forty-seven 
degrees, or the 3,266^ statute miles of the Earth's 
surface, embraced between the 23^ degrees of 
north and 23£ degrees of south latitude, constitute 
the bulkiest part of the globe, under the powerful 
rays of the Sun. 

Q. This being the case, what effect is produced 
upon the Earth % 

A. The torrid regions receive the greatest 
amount of electricity, and, through them, the 
Earth is filled with it, and becomes a magnet. 

Q. At what points of the Earth' s surface does 
its internal magnetism naturally radiate and flow 
out? 

A. From the negative portions of the Earth, 
especially through the magnetic poles — the points 
of the greatest cold, both North and South. 

Q. What other reason is given why the one is 
positive and the other negative. 

A. Because the torrid regions receive the rays 
of the Sun more vertically than the other. 

Q. What application can be made of this infal- 
lible rule 1 

A. The equatorial regions being positive and the 



polar being negative, there is a mutual attraction 
of the positive, or the superabundant fluid of the 
one and the negative of the other. 

Q. Upon what principle is this clearly understood? 

A. On the immutable and universal chemical 
principle, viz. : that opposite properties, or a posi- 
tive and a negative, always attract, or that coloric 
always seeks to keep up an equilibrium, or to 
restore it when disturbed. 

Q. What is the result % 

A. That there are actually two forces operating 
upon the superabundant electricity or caloric of 
the equator. 

Q. What is then the consequence of the com- 
bined action of the two forces ? 

A. Why, there will be two strong currents of 
electricity rushing continually with lightning 
speed form the points of the greatest cold, or the 
magnetic poles, instead of the geographic poles, 
to the equator. 

Q. Now, will you give us an explanation of 
magnetic attraction % 

A. It is evident that currents of electricity 
influence the needle, and the reason why the 
North Pole guides the needle north of the equa- 
tor and the South Pole, when south of the equator, 
is, that these currents of electricity, rushing from 
the poles upward, constitute what is called terres- 
trial magnetism. 

Q. What effect do these currents have upon the, 
needle ? 

A. They give direction to the needle of the com- 
pass, and, as the point of the greatest cold varies, 



ELECTRO-ASTRONOMICAL ATLAS. 



so these currents vary, and as they vary, so the 
needle varies. 

Q. Were the geographic pole of the Earth the 
point of attraction, what effect would it have on 
the needle ? 

A. It would never vary at all, but as it is, it 
varies both diurnally and annually. 

Q. Why is this so % 

A. Because there are causes always operating 



at the North Pole to change the point of the 
greatest cold, particularly in the summer season, 
when the floating icebergs or ice islands of the 
Arctic are continually changing their position. 

Note. — There are other hitherto mysterious 
phenomena which can be rationally and philo- 
sophically accounted for only on the supposition 
that such currents of electricity exist, as we have 
described. 



LESSON LX. 
Aurora Borealis. 

Analysis. — How produced — Caloric and Electricity the same — Currents within the Earth naturally seek the point of the greatest 
cold, flow out and form a lambent waving light — Called Aurora — This illustrated — Historic evidence — Captains Parry and 
Ross — Their testimony — The ultimate conclusion — This clearly explained — Power of Terrestrial Magnetism controls the 
Moon — On the principle of Attraction and Repulsion — The same law by which the Sun governs the Planets and they their 
Secondaries in the Solar System. 



Q. How are the phenomena of the Aurora 

Borealis and Aurora Australis, the Northern and 
Southern Lights, produced? 

A. Now, if caloric and electricity be the same, 
of which there is no doubt, then these currents, 
issuing from within the Earth, naturally seek the 
point of the greatest cold, in the frigid zone. 

Q. When it arrives at that point, what becomes 
of this electric fluid % 

A. It streams up into the rarer regions of the 
atmosphere, and, in its return to its original 
source, it spreads out into the lambent, waving 
light, exhibited by Aurora. 

Q. How is this illustrated % 

A. The appearance being precisely the same as 
electricity exhibits in passing through an ex- 
hausted tube — the same cause — the rarity of the 
atmosphere, operating in both cases, to produce a 
luminous, waving cloud, which proves that they 
must be identical. 



Q. What historic evidence have we that these 
positions are tenable ? 

A. Captains Parry and Ross, in their expedition 
to discover the North-west passage, ascertained that 
the focal point from which streams upward the 
Aurora Borealis, was exactly the point of mag- 
netic attraction. 

Q. What conclusive evidence did \hsy obtain % 

A. That when drawing near that point, the dip- 
ping needle stood exactly perpendicular, while 
the horizontal needle would not traverse at all, but 
would remain in any position in which it was 
placed. 

Q. What other important fact did they dis- 
cover ? 

A. They ascertained also, what we have hereto- 
fore maintained, that this point of attraction was 
comparatively that of the greatest cold. 

Q. From this investigation and this course of 
reasoning, what is the ultimate conclusion ? 



ELECTRO-ASTRONOMICAL ATLAS. 



87 



A. That' caloric streams down from the Sun, 
deeply electrifies the equatorial regions, penetrates 
the Earth, rendering it entirely magnetic, and that 
its internal magnetism seeks an egress through 
the points of the greatest cold, streams upwards 
as it passes out from the magnetic poles, rises into 
the rarer or thinner regions of the atmosphere, 
and, like electricity in its passage through the 
exhausted tube, spreads out into a waving, lumi- 
nous cloud, and forms the Aurora Borealis at the 
north, and the Aurora Australis at the south. 



Q. How is it that the Earth holds the moon 
steady in its orbit, while revolving around it % 

A. The Earth, having been made a magnet by 
the electrical power of the great galvanic battery, 
the Sun, now by its terrestrial magnetism, controls 
the moon in its revolution, on the principle of 
attraction and repulsion, the same law by which 
the Sun governs all the planets and they their 
secondaries in the Solar System. 



LESSON LXI. 
Attraction and Repulsion. 

Analysis. — Subject defined — Law governing — Ultimate particles have opposite polarities — Law manifest — Laws of the whole are 
the laws of its parts — By this rule only can Attraction and Repulsion be accounted for — Magnetism and Electricity considered 
the same agent — Galvanism differs only in the mode of exhibition — Experiment — Result from passing a current of Galvanism 
through Soft Iron ; change the poles of Battery — Change the polarity of the Iron — This explained — Distinction of polarity 
manifest in the direction of the current — This explained — Positive and negative end to everything — Running electricity — The 
inward current always negative — The outward current positive — Remark. 



Q. Now, what is the solution of the apparent 
difficulty \ 

A. It is this, every ultimate particle of electricity 
has opposite polarities, that is, each end of each 
individual particle has a different property ; like 
ends, or polarities, repel, and unlike ends or 
polarities attract. 

Q. What immutable truth is clearly evident 
from this position ? 

A. That the laws of the whole are the laws of 
its parts. 

Q. By the operation of this rule, what phenom- 
enon can be rationally accounted for ? 

A. The phenomenon of Attraction and Repul- 
sion among both atoms and planets. 

Q. What is the difference between electricity 
and galvanism ? 

A. They are generally conceded to be the same 



agent — galvanism differs only in the mode of its 
exhibition. 

Q. What is the result if you pass a current of 
galvanism around soft iron, bent in the shape of a 
horse shoe, wound with insulated copper wire % 

A. You make the iron magnetic, and the two 
ends have different polarities. 

Q. What is meant by different polarities. 

A. That one is negative and the other positive, 
or, what one end attracts, the other will repel. 

Q. Suppose we change the poles of the battery, 
and pass the current of electricity in the opposite 
direction around the spiral wire, what will be the 
result ? 

A. There will be a change in the polarity of the 
iron, and make the end that was positive, negative, 
and the end that was negative, positive. 

Q. How can this be clearly shown ? 



88 



ELECTRO-ASTRONOMICAL ATLAS. 



A. It can be shown by experiments in electro- 
magnetism. 

Q. Upon what, then, does a positive and nega- 
tive state evidently depend ? 

A. They entirely depend npon the direction in 
which the current runs. 

Q. What distinction of polarity is manifest in 
the direction of the current % 

A. The end, where the current passes inward, 
is always negative, and the end where it passes 
outward, is always positive. 

Q. What reason have we for this phenomena? 

A. It is readily found in the admirable rule 
"that the laws of the whole are the laws of its 
parts." 

Q. If by running a current of electricity in a 



certain direction, we make one end of a bar of iron 
positive and the other negative, what must be the 
polarity of each individual particle ? 

A. Each particle must have a positive and a 
negative end. 

Q. In the passing of the current, how are we to 
distinguish the polarity % 

A. The positive end is always leading, and the 
negative, of course, always following. 

Q. Why should we naturally infer this % 

A. From the fact that the laws of the whole are 
the laws of its parts, and the laws of its parts are 
the laws of the whole. 

Remark. — It would be utterly impossible -that 
the whole of a thing should have a quality the 
opposite of the parts of which it is composed. 



LESSON LXII. 

Attraction and Repulsion — Continued. 

Analysis. — Another mode of illustration — Currant of Galvanism passed around Steel — Result — A magnet — Cut the Steel in 
pieces — Each arranged with the same polarity of the whole — Logical inference — Conclusively evident — How illustrated — 
By the atmosphere and ocean. 



Take Another Illustration. 

Q. Suppose we pass a current of galvanism 
around a bar of steel, spirally, in the same man- 
ner it is passed around soft iron, what will be the 
consequence ? 

A. We make it permanently magnetic, the end 
where the current enters is negative, and the end 
that is outward is positive, and so it will remain 
for years. 

Q. Now should we cut that bar of steel in ten 
thousand pieces, what would be the polarity of 
each piece ? 

A. Each piece would have a positive and a nega- 
tive end, and the positive and negative polarities 



of the pieces will be arranged in the same direction 

as in" the whole. 
Q. What then is the unavoidable and logical 

inference ? 
A. That each ultimate particle of electricity 

which made it magnetic and kept it magnetic has 

opposite polarities, as well as the whole current. 
Q. Why is this conclusively evident % 
A. Because the polarities of the whole are most 

assuredly made up of the properties of its parts. 
Q. How may this be clearly illustrated % 
A. A mere thimble-full of atmosphere contains 

its proportion of oxygen and nitrogen, as well as 

the whole mass. A drop of water contains its 



ELECTRO-ASTRONOMICAL ATLAS. 



8!) 



relative proportion of oxygen and hydrogen as 
well as the ocean — and so with every thing else. 

Remark. — The question as to what is the real 
cause of attraction and repulsion is one that has 
not been clearly understood, and hence has not 
heretofore been satisfactorily explained. 

Electricity has been esteemed so mysterious and 
complicated in its operations that there has been 



a hesitancy to investigate its laws, or, if such 
investigation has been made, there has been a 
reluctance to express the opinions entertained 
respecting them, for fear those opinions would 
become a subject of ridicule to the Scientific World: 
These laws, when fully understood, clear up the 
mystery. 



LESSON LXIII. 



Attraction and Repulsion — Continued. 

Analysis. — This theory explained — Two magnets — Effect when Positive and Negative are presented to each other — They attract 
— Result when like polarities are presented — Entirely opposite ; they now Repel each other — Two Positives repel — A Positive 
and Negative attract each other — Scientific World challenged to give a clear explanation on any other principle — A body charged 
with electricity has an outward current, and will attract a negative with an inward current — Clearly shown by the magnets — 
These laws applied in the Attraction and Repulsion — How accomplished. 



Q. Our first inquiry is, will not the above theory 
explain the phenomena of attraction and repul- 
sion? 

A. We think the facts above stated are true, 
and can be fully and satisfactorily illustrated. 

Q. How can this principle be easily and scien- 
tifically explained ? 

A. Take two steel magnets, with equal power, 
let them be dipped in iron filings until they have 
accumulated as large an amount as they can 
retain upon their poles, and the opposite poles of 
each be presented within a short distance of each 
other, the filings will spin out and fill up the 
space between them, and present an oily, ropy 
appearance. 

Q. What will be the consequence if we change 
and let like poles be presented ? 

A. Then the filings will be blown back, as it 
were, and stand out like hair around the points of 
the magnets. 

Q. Now what does this indicate ? 



A. It shows that there is attraction in the former 
case and repulsion in the latter. 

Q. Does not the admission of this principle and 
its explanation show conclusively that electricity 
must be the controlling power in attraction and 
repulsion ? 

A. We cannot see how "two positives repel, 
and a positive and a negative attract" can be 
explained on any other principle, and challenge 
the Scientific World to give another. 

Q. Why is it that a body charged highly with 
electricity, has an outward current, and will attract 
one that is negative, with an inward current ? 

A. Because it has been shown by the magnets 
that the body thus charged always presents its 
positive end, and the body, negative, with an in- 
ward current, is attracted, and presents its negative 
end to the positive. 

Q. What is clearly indicated by this representa- 
tion? 

A. That these two bodies, one having an out- 



90 



ELECTRO-ASTRONOMICAL ATLAS. 



ward and the other an inward current, present 
opposite polarities to each other, and are attracted 
from the immutable law, that opposite polarities 
attract. 

Q. Now suppose we apply these laws of attrac- 
tion and repulsion, as exhibited by the magnets, 
to the planets \ 

A. We have a correct solution of the apparent 
difficulty. 



Q. How is this accomplished ? 

A. The Sun, being positive, pouring a flood of 
light upon one portion of a planet, soon renders 
that portion positive, hence, is repulsed by the 
Sun, while the other portion, being negative, is 
attracted by the Sun, thus clearly illustrating the 
principle of repulsion and attraction, by the un- 
changeable law that two positives repel, and a 
positive and negative attract each other. 



INSTRUCTION TO TEACHERS. 91 



INSTRUCTION TO THE TEACHER IN THE- USE OF THE DIAGRAM AND IN 

POINTING OUT AND EXPLAINING THOSE PRINCIPLES THAT 

PERTAIN TO THE MOTION OF THE PLANETS. 



In teaching, the teacher should have the pupils recite in concert the Tabular view. 

When they become familiar with that, then point to any planet in the Solar System, and 
ask how far that planet is from the Sun. Soon as they observe where the teacher points, and 
sees the name of the planet, they will know how far it is from the Sun ; having learned it in 
the Tabular Table, at the same time they can see the Sun, as the grand center, around which 
the planets moved. This enables the pupil to associate the idea with the form, and conceive 
in his mind distance. 

II. 

The teacher, as he asks the questions laid down in the lesson, will point to the planet 
about which he is asking questions. 

III. 
When he speaks of the distance the planet is from the Sun, he will convey to the mind 
of young scholars a more clear idea of distance by moving his pointer from the Sun to the 
planet of which he speaks. 

IV. 

When he asks how long it takes a planet to make a revolution around the Sun, he 
should hold his pointer even with the axis of the planet, inclined in the same way with it ; 
and as he moves it around the Sun from west, to east, he gives an idea of yearly motion. 

V. 

In showing the cause of equal day and night, the teacher will show the pupil how the 
Earth is represented in the Diagram on the 21st of March and the 23d of September. Show 
him that the Sun then strikes vertical at the equator, and shines from pole to pole, illumi- 
nating the whole side of the Earth, while the side from the Sun is dark, as represented in the 
Diagram. ' 

VI. 

Then to show why the days grow longer and the nights shorter, he can illustrate it from 
the Diagram, that as the Earth moves from her place in March to the one she occupies in 
June, the north polar circle is advancing further into the light, and the south polar circle is 
receding into the dark, to a corresponding extent, at the same time. Then, by holding the 
pointer parallel with the equator, the part of the Earth above the pointer will show how 



92 INSTRUCTION TO TEACHERS. 



much of the Northern Hemisphere is enlightened, and the part below the pointer will show 
how mnch of the Southern Hemisphere is enlightened, so that when the days are growing 
longer north of the equator, they are growing shorter south of the equator ; and while the 
days are growing shorter in the Northern Hemisphere, they are growing longer in the 
Southern Hemisphere ; the same may be shown of the nights. 

VII. 

The teacher will give a correct idea to the pupils why it is winter in the Southern 
Hemisphere while it is summer in the Northern, by placing his pointer parallel to the equa- 
tor, so as to show that a great part of the Northern Hemisphere is continually in the light 
of the Sun, while at the same time so little of the Southern Hemisphere is enlightened. 

VIII. 

Again, he can show by placing his pointer on the equator in the same way as before, 
that the inhabitants south of the equator have the same season of the year that we have 
north, when the Earth arrives in the exact opposite point of the orbit. For instance, on 
the 21st of December they have the same season that we do when the Earth reaches that 
point of her orbit designated as on the 21st June^ for in every opposite point of the Earth's 
orbit, the same is represented in the Diagram, showing as much enlightened north of the 
equator as is enlightened in the opposite point of the equator. 

ECLIPSE. 

In explaining the causes of an eclipse, the teacher can show by his book or his pointer, 
its shadow. The pupil will perceive that a body always casts its shadow in the opposite 
direction from the light. 

Then as the Sun is the great source of light, the Earth is represented as casting her 
shadow in the opposite direction from the Sun. 

IX. 

The Diagram represents the moon in the Earth' s shadow, which causes it to be eclipsed. 
The teacher will be particular to show the pupils the manner in which the Moon is enlight- 
ened by the Sun, and that the rays of incidence and reflection are in equal angles ; so that 
rays of light from the Sun that strike upon the moon are reflected to the Earth in like angles, 
causing the side of the moon toward the Earth to show a constantly expanding crescent 
from new till full moon, then a continuous wane, till no rays from the Sun can be reflected 
to the Earth from the moon, as she is at new moon, between the Earth and the Sun. 

X. 

The teacher will point out the path or orbit in which the Earth moves around the Sun, 
and show them that its circumference is 600,000,000 miles, and as the Earth flies through 
this space once every year, in the period of one month she will move one-twelfth of 600,000,- 
000 miles, which is 50,000,000, and the north polar circle has advanced a little further into 
the light, from the 21st of March, as represented in April on the Diagram ; and by holding 
his pointer just as the axis of the Earth is inclined, and passing it along round toward June, 
can show how many million miles the Earth moves from her place in March, before the north 
polar circle is wholly in the light and the south polar circle is entirely in the dark, which is 



INSTRUCTION TO TEACHERS. 93 



150,000,000 miles, and as the axis points always in the same direction in the heavens, of 
course the south pole will remain in the dark while the Earth moves 150,000,000 miles still 
further, showing why we have six months day at the north pole, and night during the same 
time at the south pole. Then the south pole begins to come into the light, and remains in 
it from the 23d of September until the 21st of March, and the north pole is in the dark dur- 
ing the same time, showing why we have in turn six months day at the south pole, and night 
during the same time at the north pole. 

XL 

Reference to the diagram should be made whenever the teacher can associate an idea 
with the form, especially with the beginner in the study of Astronomy, for nothing is better 
calculated to call forth and develop the reasoning faculties of the young scholar than to asso- 
ciate ideas with forms. 

XII. 

Again, these principles that pertain to the motions of the Earth are principles that 
prompt the first inquiry of the pupil, and are most difficult of explanation by the teacher. 

XIII. 

It is not only important that the education the youth receives should be virtuous and 
purely moral, flowing from well cultivated minds, but it is equally important that it should 
be correct, and an occular demonstration will render those principles clearer to young 
scholars, without which their imagination cannot be stretched to make them understand 
without going beyond their capacity. 



APPENDIX 



TABLE I.— ELEMENTS OF THE SOLAR SYSTEM— (Sun's Parallax, 8.94"). 



Sun 

Mercury 
Venus . 
Earth . . 
Mars. . . 
Jupiter 
Saturn. 
Uranus 
Neptune . 
Moon 



Mean 
Diameter. 



852,900 

2,962 

7,510 

7,912 

4,300 

85,000 

70,100 

33,247 

36,806 

2,162 



Mass, Earth 
being one. 



315,000 
.063 
.885 
1. 
.118 
301. 
90. 
12.65 
16.8 



in 



5.84 

5.67 

3.97 

1.37 

.74 

.97 

.91 

3.4 



Mean Distance 
Millions. 



35.4 
66.15 
91.5 
139.3 

475.75 

872. 
1,754. 
2,746. 



.205 

.0069 

.017 

.093 

.048 

.056 

.047 

.0087 

.055 



7° 
3£° 



1°51' 
1°19' 
2°30' 
46*' 
1°47' 
6? 



Sidereal Period. 



1 
11 

29 

84 

164 



224| 
365i 
322 
315 
167 
6 
226 
27£ 



1 ° 



116 

584 

780 

399 

378 

369* 

367| 



Time of 
Rotation. 



25 d. 8 h. 

23 h. 56 m. 

23 h. 21m. 

24 h. 

24 h. 37 m. 
9h. 55* m. 

10 h. 29 m. 



27* d. 



Inclination 

of 

Axis. 



7° 20' 



75° 

23° 28' 

28° 42' 

3° 6' 

26° 49' 



TABLE II.— ELEMENTS OF THE MINOR PLANETS. 



Flora 

Ariadne 

Feronia . . . 
Harmonia . . 
Melpomene 

Sappho 

Victoria. . . 
Euterpe . . . 

Vesta 

Urania 

Nemausa. .. 

Clio 

Irts 

Metis 

Echo 



"a 


IT 




8 


Earth's— 1 
2.2014 


.157 


43 


2.2034 


.168 


71 


2.2661 


.12 


40 


2.2677 


.046 


18 


2.2956 


.217 


80 


2.2963 


.2 


12 


2.3344 


.219 


27 


2.3467 


.173 


4 


2.3733 


.09 


30 


2.3655 


.126 


52 


2.3657 


.066 


84 
7 
9 


2.3675 
2.3862 
2.3866 


.238 
.231 
.123 


62 


2.393 


185 



150 
151 
174 
175 
207 
217 
229 
223 
223 
225 
240 
251 
256 



Hind 

Pogson ,. . . 

C. H. F. Peters 
Goldschmidt. . . 

Hind 

Pogson 

Hind 

Hind 

Olbers 

Hind 

Laurent 

Luther 

Hind 

Graham 

Ferguson 



1847 
1857 
1861 
1856 
1852 
1864 
1850 
1853 
1807 
1854 
1858 
1865 
1847 
1848 









APPENDIX. 




95 


TABLE II.— 


ELEMENTS 


OF THE MINOR PLANETS — Continued. 




Name. 


a 
1 


5g 
3 


a 




Jo 

fl o 


~ 1 


Discoverer. 


A 


Atjsonia 


63 
25 
20 

67 
44 
6 
83 
21 
42 
19 
79 
11 
17 
46 

29 

13 
5 

14 
32 
91 
47 
70 
54 
78 
23 
37 
15 
51 
66 
85 
26 
73 

3 

75 
77 
64 
34 
58 
55 
60 
45 
38 
36 
72 
56 
82 

1 
39 
41 

2 
88 
74 
28 

81 
33 
48 
22 
16 
68 
59 


Earth's—I 
2.395 
2.4008 
2.4097 
2.4217 
2.422 
2.4259 
2.4287 
2.4354 
2.44 
2.4411 
3.4431 
3.4519 
2.4735 
2.5265 
2.5498 
2.554 
2.5766 
2.5771 
2.586 
2.5873 
2.5958 
2.5959 
2.6133 
2.6197 
2.6228 
2.6271 
2.6414 
2.6437 
2.6491 
2.6513 
2.6536 
2.6561 
2.6666 
2.6684 
2.6698 
2.6719 
2.6809 
2.6863 
2.7003 
2.7123 
2.7131 
2.7212 
" 2.7401 
2.7461 
2.7554 
2.7591 
2.7603 
2.7667 
2.7671 
2.7691 
2.7696 
2.7702 
2.7777 
2.7785 
2.7804 
2.8563 
2.8641 
2.8812 
2.9107 
2.9237 
2.9717 
2.9848 


.126 
.254 
.144 
.185 
.151 
.203 
.084 
.162 
.225 
.158 
.195 
.099 
.128 
.164 
.18 
.074 
. .087 
.187 
.166 
.083 

!237 

.183 

.204 

.205 

.233 

.177 

.187 

.287 

.158 

.191 

.087 

.043 

.357 

.307 

.136 

.128 

.107 

.042 

.197 

.117 

.08 

.155 

.301 

.174 

.145 

.226 

.08 

.115 

.266 

.24 

.165 

.238 

.15 

.188 

.212 

.339 

.132 

.098 

.135 

.174 

.162 


5 47 
21 35 
41 
5 59 
3 42 

14 47 
5 2 

3 5 

8 34 

1 33 

4 37 

4 37 

5 36 

2 18 
16 11 

6 8 
16 31 

5 19 

9 8 
5 29 

*8 i 

11 38 
5 7 
8 38 

10 13 

3 7 

11 44 

2 48 

3 4 
11 53 

3 36 
2 25 
13 1 
5 
2 28 

1 20 
5 26 

5 2 
11 47 

8 37 

6 35 

6 58 
18 42 
23 19 

7 14 

2 51 
10 36 
10 22 

15 59 
34 43 

5 15 

3 59 

9 21 
7 57 

7 55 
1 56 
5 

13 44 
3 4 

8 28 
18 15 


Yrs. Dys. 
3 258 
3 263 
3 270 
3 280 
3 281 
3 284 
3 287 
3 292 
3 296 
3 297 
3 299 
3 306 

3 325 

4 6 
4 26 
4 30 
4 50 
4 51 
4 58 
4 59 

4 67 

4 82 
4 88 
4 90 
4 94 
4 107 
4 109 
4 114 
4 116 
4 118 
4 120 
4 129 
4 131 
4 133 
4 134 
4 142 
4 147 
4 160 
4 171 
4 172 
4 179 
4 196 
4 201 
4 209 
4 213 
4 214 
. 4 220 
4 221 
4 223 
4 223 
4 224 
4 231 
4 232 
4 233 
4 302 
4 309 
4 325 

4 353 
5 

5 45 
5 57 




1861 
1853 
1852 
1861 
1857 
1847 
1865 
1852 
1856 
1852 
1863 
1850 
1852 
1857 
1866 
1854 
1850 
1845 
1851 
1854 
1866 
1857 
1861 
1858 
1863 
1852 
1855 
1851 
1857 
1861 
1865 
1853 
1862 
1804 
1862 

1861 
1855 
1800 
1858 
1860 
1857 
1856 
1855 
1861 
1858 
1864 
1801 
1856 

1802 
1866 
1862 
1854 
1861 
1864 
1854 
1857 
1852 

1861 
1860 






De Gasparis 




Ntsa 




















Hind 




















Amphitrite 












Hind 






















Diana 




Hind 














Maia 


H. P. Tuttle 


Io 










Tuttle 








































Cliacornac 






















Chacornac 






Olbers 


Thisbe 


Tempel 
























Hind 



















96 APPENDIX. 


TABLE II.— ELEMENTS OF THE MINOR PLANETS — Continued. 


Name. 


l 
& 


3e 

ii 






fe £ 


Discoverer. 


1 


Leucothea 


35 
50 
86 
53 
49 
90 
61 
24 
10 
31 
57 
76 
65 
87 
92 
93 
94 
95 
96 
97 
98 
99 
100 
101 
102 
103 
104 
105 
106 


Earth's^l 
3.0060 
3.0825 
3.0908 
3.0999 
3.1094 
3.1188 
3.1297 
3.1431 
3.1511 
3.1527 
3.1565 
3.3877 
3.4205 
3.4927 


.217 

.237 

.205 

.004 

.077 

.148 

.169 

.117 

.1 

.22 

.104 

.188 

.12 


8 12 

3 9 

4 48 
7 25 
6 29 
2 16 

2 12 
49 

3 49 
26 27 
15 8 

2 2 

3 28 


Yrs. Dys. 
5 78 
5 150 
5 158 
5 168 
5 176 
5 186 
5 196 
5 209 
5 217 
5 218 

5 222 ■ 

6 86 
6 119 
6 193 




1855 
1857 
1866 
1858 
1857 
1866 
1860 
1853 
1849 
1854 
1859 
1862 
1861 
1866 
1867 

1868 


Goldschmidt 






Goldsckmidt 






Lixtlier 


Erato 










Ferguson 

Lutlier 

D' Arrest 

Tempel 

Pogson 










Minerva 
















































































































5 






















Watson 


■M i 




















« 


J " 










« 














* 



PLATE XX. 




WEED, PARSONS & C9.ALBANY. 



A.TOLLE, PHOTO. LITH. 



THE GREAT EQUATORIAL 

(PARIS OBSERVATORY.) 



